A. One who goes out during the days of Nisan and sees trees that are producing blossoms says: Blessed are You, Lord our God, King of the Universe, who has not withheld anything from His world and has created within it good creatures and good trees for people to enjoy. Rav Eliyashiv ruled that even women and children should recite this blessing, and it is fitting that there should be two trees, as stated in the blessing.

B. Hurry to provide Passover flour, as explained in the Rema: "And it is customary to buy wheat to distribute to the poor for the needs of Passover." The Mishnah Berurah writes about it: "And in our countries, the custom is to distribute flour to them." Today, money is given instead. The reason for the necessity of this enactment is explained in Sha'ar HaTziyun: It is possible that because of this, our ancestors enacted more in Passover than the other festivals, as it is a time of freedom, and people recline and everyone, he and his household, are in great joy. It is not honorable to God that the poor should be hungry and thirsty then, so flour is given to him throughout the days of Passover so that he too can recount the exodus from Egypt joyfully.

And Rabbi Yosef Shalom Elyashiv ruled that if one knows that a relative needs Passover flour, they must prioritize providing it for them. Refer to Ma'adanei Shlomo and the rulings: it is permissible to provide Passover flour from tithe money. And Rabbi Yosef Shalom's opinion is to give a little from one's personal money and the rest from tithe money.

C. It is the custom of the rabbis to deliver a sermon before the congregation on the Great Sabbath. The main purpose is to instruct the people in the ways of the Lord, to teach them the practices they should perform, namely the laws of cleaning, removing leaven, baking matzah, and other Passover laws.

D. On the Great Sabbath, it is customary to recite the Haggadah from "We were slaves" to "to atone for all our sins." However, the Vilna Gaon did not follow this custom, and his reasoning is because it is stated in the Haggadah, "One might think from the outset, etc."

It appears that there is no definitive decision on how to act practically. It seems that each person should adhere to the custom of their ancestors, as it is implied by the Rema that this matter depends on custom. Consequently, if this custom is not established among them, one should not follow it either, in order to fulfill the opinion of the Vilna Gaon that it should not be said. In this way, one fulfills the obligation of all opinions.

1. At the beginning of the night of the 14th of Nisan, one should check for leaven by candlelight, in cracks and crevices, in all places where leaven may have been brought. Immediately after the stars appear, while there is still some daylight remaining, it is appropriate to begin the search so as not to neglect or forget. It is important to commence the search promptly at nightfall, according to the opinion of Rabbi Abraham ben David. However, according to the view of Rabbeinu Gershom, the time begins at sunset. The author of "Hagahot Chatam Sofer" writes that it is possible to act in accordance with the need.

2. If one wishes to delay the search for a period of time due to various reasons, it may be beneficial to appoint someone to remind and encourage them to perform the search, thus alleviating the concern stated in the Mishnah Berurah, or because since the Sages already established the order of the search in this manner, it should not be changed even if the concern that led to this arrangement no longer applies. Further inquiry is required.

3. If one checked on the 13th day, they should check again on the night of the 14th without a blessing. If one checked on the night of the 13th and found leaven, they may check again on the night of the 14th without a blessing.

4. Everyone should be cautious not to engage in any work or eat before conducting the search. Even if one has a set time for studying, they should not study until they have conducted the search. Some prohibit even studying half an hour prior. A casual taste is permitted, such as a piece of bread the size of an egg or less, or fruits, even many.

5. Those who pray the evening service in a congregation should pray earlier, as it is burdensome for the congregation to gather afterwards.

6. It is advisable to clean the rooms of the house before the search, preferably from the 13th day.

7. It is customary to place crumbs of leaven where one will search to ensure that the blessing is not in vain. However, if one did not place them and did not delay, it is not a hindrance, as every individual has the blessing to nullify it if found. They should be hard crumbs that do not crumble, and in a place protected from infants and rodents. If no crumbs were placed and no leaven was found during the search, the vessel designated for collecting leaven should be burned if it is made of wood, as per the mitzvah of removal.

8. It is correct to ensure that the crumbs are smaller than a kezayit, but collectively they should amount to a kezayit. If, after checking all the rooms and nullifying, one realizes that one of the crumbs is missing, there is no need to return and check all the rooms again, it is sufficient to nullify after one.

9. There is a debate among the authorities whether it is possible or even preferable to check using a flashlight. In the name of our teacher, Rabbi Aharon zt"l, it is said to start with a candle and continue with a flashlight.

10. Even if one missed checking on the night of the 14th, when checking on the 14th day, they should not check by sunlight but by candlelight.

11. During the search, it is customary to take a feather and carefully inspect the cracks and crevices to remove leaven, and to collect the crumbs with a spoon.

12. It is advisable to also check pockets and to return and shake them out during the removal.

13. Offices and cars require inspection but can be checked initially on the 13th day without a blessing.

14. One can check multiple houses with one blessing, even if they have separate courtyards.

15. The blessing formula for the search is: "Upon the removal of leaven." Even though it is not being burned until the next day, since this search is for the purpose of removal, it is considered as if it has been removed. Therefore, the blessing should also include the removal that will occur the next day.

16. One should be careful not to speak between the blessing and the beginning of the search. It is best not to speak about other matters until the entire search is completed so that one focuses on checking all the places where leaven is brought in. However, if one spoke, there is no need to return and recite the blessing, as the mitzvah has already begun. Matters related to the search can be spoken about.

17. After the search, one should be careful with the leaven they are setting aside to burn it discreetly so as not to require another search, such as if a mouse touches it, or if some of it is missing.

18. Regarding what is considered leaven and how much requires inspection - initially, crumbs are not considered leaven. However, in a slightly larger quantity than crumbs, there is a slight concern of being considered leaven. In practice, crumbs are also treated stringently because Israel are holy.

19. One should set aside at least a kezayit of leaven to fulfill the mitzvah of burning it the next day. If one has no leaven left, they should acquire some from another, to fulfill the mitzvah.

20. It is advisable to purchase leaven for one's adult children so that they can fulfill the mitzvah of removing leaven.

21. If one is leaving for the entire holiday period to their parents' home or similar, if they leave before 30 days before the holiday, they should nullify at the appropriate time, and if within 30 days, they should check on the night before their departure. Accordingly, young men leaving home between the times should check their rooms before leaving, without a blessing. If one sells a room in their apartment to a non-Jew, some obligate to check it since during the time of the inspection, it is still not in the possession of the non-Jew, while others exempt from checking since the sale itself is also a mitzvah of removing leaven.

22. If one leaves before the holiday from a non-Jewish house, there is no need to check before leaving, and they can fulfill the mitzvah of removing leaven in the house they enter. If the homeowner is present, one can have them fulfill this mitzvah on their behalf as a proxy or rent the room from them.

23. The homeowner can bless on the inspection of several houses, and those listening to his blessing can be his agents for inspecting other houses. Ideally, one should rely on individuals who are obligated in the mitzvot, namely those who are over 13 years old, as the inspection involves significant effort, and there is a concern that they may become lazy and not inspect properly.

This text provides detailed guidelines for the traditional Jewish ritual of searching for leavened bread before the Passover holiday, including when and how to conduct the search, the blessings to be recited, and various customs and considerations associated with the process.

1. The custom is to fulfill the mitzvah of chametz removal by burning, and during the day, before the sixth hour, while the chametz is still in one's possession, and afterward to nullify the chametz. No work or eating should commence until it is burned. It is permissible to benefit from the coals even during Passover. If it is burned with oil, one should be careful not to invalidate it with oil before the burning. One should declare "All leaven in my possession is nullified" only after the chametz has been burned, as otherwise, the burning of his chametz is not fulfilled.

2. If one casts the chametz into an ownerless place and abandons it verbally and mentally, he is exempt from the obligation of removal.

3. If one casts the chametz into the garbage, it still needs to be invalidated, even in a communal garbage bin or a place where non-Jews reside, because a non-Jew does not acquire a courtyard, and it is precise.

4. If chametz is found in one's home after its prohibition time, he should hasten to burn it with fire, and if it is sold to a non-Jew, he should not burn it but should create a partition for it so it will not come to be eaten.

5. After the time of chametz prohibition, one should not touch chametz with his hands.

1. If leaven becomes mixed after the time of its prohibition with something unsuitable for human consumption, it is forbidden to eat it. However, if it became nullified before Passover, it is permissible to derive benefit from it, and some permit its consumption as well.

2. Bread that became disqualified for consumption by a dog does not need to be burned; it is permissible to derive benefit from it, but it is forbidden to eat it because it is considered food for the dog.

3. It is permissible to use non-Jewish leaven for healing purposes if there is no other remedy available, and everyone should follow their custom in this matter.

4. Stubborn leaven, such as dough whose surface has dried but has not cracked, or dough not suitable for consumption, or flour mixed with water used as adhesive for papers, must be burned rabbinically. However, one does not transgress the prohibition of "seeing or finding" leaven with it. Regarding a cloth with wheat starch (wheat gluten), some are stringent not to use it, lest it disintegrate into the food, and some are lenient. This is also what I have received from my teachers.

5. The reason for the severity of the prohibition of leaven is that it alludes to the evil inclination. It is stated in the writings of the Ari, may his memory be blessed, that one who is careful about leaven during Passover is assured not to sin throughout the year.

6. There are additional customs of stringency:

1. Not eating carp fish because they put a spirit on it. However, nowadays this is not done, so we are lenient about it.

2. Not mentioning leaven in one's mouth on Passover.

3. Not drinking brandy because it is difficult to make it kosher for Passover.

4. There are places where people are stringent not to eat dried figs and raisins, and some are lenient. In these countries, they have the custom of being stringent not to eat any dried fruits unless it is known that they were dried in a way that does not pose a concern for leaven, such as if it is known that they were dried in the sun or in an oven after being checked for leaven.

5. Some eat only fruits that can be peeled.

6. Some do not eat potato flour because it resembles regular flour.

7. Some refrain from using oil produced in a pottery.

8. Some refrain from using a fork or similar utensil that fell on the floor.

1. Matzah used for the Seder night, which is prohibited to eat throughout the day on the 14th [of Nisan]. This prohibition begins at dawn. A child who does not understand the story of the Exodus may be fed matzah, and there are customs not to eat matzah from the beginning of the month. Recent authorities have written that swollen or folded matzah, although treated stringently as leavened bread, is nevertheless forbidden to eat from dawn onwards, as it is considered matzah fundamentally. Rabbi Yosef Karo ruled that only matzah suitable for the mitzvah is included in this prohibition, and if one needs secondary bread, it is permissible to eat any kind of matzah.

2. Matzah baked properly and later cracked, mixed with wine and oil, even if baked again, is not called rich matzah, and it is forbidden to eat it on the eve of Passover.

3. If it is cooked, as is the custom in our countries to make dumplings from matzah called "knaidlach," or from matzah boiled in the first vessel, it is permissible to eat it before the tenth hour, as it is certainly not called matzah.

4. It is permissible to eat bread and rich matzah before the tenth hour, and afterwards it is forbidden, so that one may eat matzah with appetite at night.

5. Some have the custom not to eat lettuce on the eve of Passover in order to eat bitter herbs with appetite, and similarly on the first day of Passover, in order to eat on the second night with appetite, but this custom has no basis. According to this, it is possible to taste from the bitter herbs.

6. From the tenth hour, one should not drink even a little wine, because it may cause drowsiness, and it is reasonable that less than a cup or certainly more than a cup is not considered drowsy, and it is permissible. But one can drink a lot because it stimulates the appetite, and drinking two cups of a quarter or most of it should be considered a lot, and it is permissible.

7. They wake up early to go to the synagogue on the eve of Passover so that one can finish his meal before four hours [of the day].

8. The firstborn fast on the eve of Passover, whether a firstborn son or daughter.

9. Some say that even a female firstborn fasts, but this is not the custom. And it is customary for one who participates in the completion of a tractate, even if she eats from what they bring home from the completion.

10. A firstborn who finds fasting difficult, and after the fast can only eat light foods in very small amounts, and it is likely that he will not be able to fulfill the eating of matzah, bitter herbs, and drinking four cups as they should be corrected, it is better that he does not fast, and it is good that he only eats minimal things.

11. If the father is a firstborn, the mother fasts instead of her firstborn son while he is still a minor. Some authorities have written that the mother does not need to fast because the father's fast also applies to his son, and where she suffers, she may be lenient. And if the father is not a firstborn, he fasts for his son until he grows up. And if his son has not yet reached thirty days, there is no need for him to fast for him.

12. Some places have been strict not to allow the firstborn to eat at the festive meal, and some places have been lenient and allow the firstborn to eat at the festive meal. And so it is practiced today in several places in our country, to be lenient and eat even at the meal concluding a tractate.

13. It is forbidden to say regarding any animal, whether a domestic or a wild one: "This meat is for Passover," even if it is young, and also a kid or a calf, which does not seem fit for Passover, is also forbidden, for they may suspect that they consecrated its value to buy a Passover sacrifice, and when one eats it, it appears as if he is eating holy things outside [the Temple]. Instead, one should say: "This meat is for the holiday." Some authorities are stringent even regarding birds and fish, as it is possible that they consecrated them for themselves, and it is good to be cautious about this.

14. Whoever works on the eve of Passover from noon onwards, whether it is incomplete work, such as mending a torn garment, in order to earn money, or complete work, such as sewing a new garment or washing a garment, even for free and for the purpose of the holiday, they should delay him, and he also does not see a sign of blessing from that work. Regarding a non-Jew, some permit, and some prohibit, and this is the custom. But for the purpose of the holiday, it is permissible to repair his vessels or the vessels of his friend that were slightly torn even by a craftsman. And it is also permissible to write books for himself for the purpose of study.

15. On the eve of Passover before midnight, in a place where they are accustomed to work, they work. In a place where they are accustomed not to work, they do not work. And we follow the custom not to work. Specifically, complete works, but other works are permissible.

16. Whatever is permissible to do during the intermediate days of the festival, such as a lost item, or one performs an action of a layman and not of a craftsman, and it is necessary for the festival, and the like, from the rest of the things that are permissible during the intermediate days of the festival, certainly they are permissible on the eve of Passover after midnight.

17. Ironing clothes on the eve of Passover for the purpose of the holiday is permissible even after midnight, but not to create new creases.

18. Cutting one's hair after midnight, many recent authorities have agreed to be lenient, but for Jews, it is forbidden even for free, because it is a complete work. If one forgets to cut his nails before midnight, he should cut them himself or have someone else cut them for him for free.

19. It is a mitzvah to wash and shave on the eve of the festival and to wear nice clothes like on Sabbath. And after midnight, one should go to the bathhouse and immerse for the honor of the holiday.

Sa. It is customary to knead matzah for the mitzvah on the eve of Passover after six hours, which is the time for the offering of the Passover sacrifice. And on the 14th [of Nisan] when it falls on a Sabbath, knead it on the eve of the Sabbath after six hours. And one should say at the time of kneading: Any crumbs that fall during kneading and preparation, and likewise dough stuck to utensils, I nullify them so that they will be annulled before they ferment.

Seventy. The Geonim, Rabbi Aharon (may his memory be blessed) and Rabbi Moshe (may his memory be blessed), disagreed regarding the koshering of the oven.

Seventy-one. Large cooking pots that cannot be placed within another vessel and heated with boiling water should have a white-hot stone placed in them, and boiling water from the first vessel should be poured over them, making them equivalent to the first vessel. The stone should then be passed over the entire vessel. This is also the practice regarding the koshering of tables and benches. The table should be rinsed with water first so that the boiling water poured over it does not cool down. In Eliahu Rabbah, it was decided that heating with stones does not effectively kosher vessels, except for a bowl or similar utensils, as most of their use involves being rinsed from the first vessel, unlike items mostly used in the first vessel, for which this method is not effective because it does not truly equate to being a first vessel. In our humble opinion, even for a bowl or similar utensils, it is not advisable to initially use stones for heating, except in cases where it is known that the vessel has not been used in its usual manner as a first vessel.

1. Rice and other types of grains do not undergo fermentation, and it is permissible to cook them. However, the Ashkenazi custom is to be stringent and prohibit this, and it should not be changed, following the principle of 'do not forsake the teaching of your mother.' Even on the last day of Passover, one should not be lenient in this matter. It is also forbidden to make them into matzah balls. Nevertheless, in times of necessity, when a person has nothing else to eat or when someone is ill without any danger, it is permissible to cook all types of grains except for the five types of grain, and small legumes are preferred over rice, millet, and similar grains, as they are more similar to the five types of grain. It is necessary to carefully examine and clarify the grains to ensure that no kernels from the five types of grain are found in them. It is preferable to cook them initially with boiling water, as anything that can be corrected with boiling is corrected.

2. Legumes that fall into a cooked dish, and the majority of the dish corresponds to them, are not prohibited after the fact, but visible legumes should be removed and discarded. It is also permissible to light candles using oils made from legumes.

3. It is permissible to keep legumes in the house. It is also permissible to eat them on the eve of Passover, although some authorities prohibit it.

4. The custom of not eating mustard at all on Passover is like the prohibition of legumes because it is treated as a type of legume.

5. Beets are not legumes and are permissible for consumption.

6. Buckwheat, peas, lentils, and turnips are legumes. Likewise, fava beans, sesame seeds, and poppy seeds are legumes.

7. It is customary to use coffee, and it is advisable to reduce its consumption before Passover, as well as tea that has not been decided upon before.

8. Some have the custom of dedicating a pot for cooking eggs or potatoes on Passover, although this is not a common custom.

9. Legumes are permissible for enjoyment, and it is permissible to light candles with oil made from legumes even if they were crushed in a mortar previously used for grinding kernels, as they are not considered sharp.

10. Corn, soybean, and rapeseed oils are typically prohibited.

11. There is uncertainty regarding cottonseed oil; in Israel, it is treated stringently according to the rulings of Rabbi Shlomo Zalman Auerbach and Rabbi Yosef Shalom Elyashiv, while in America, it is treated leniently based on the rulings of Rabbi Moshe Feinstein.

12. Cornstarch, corn syrup, dextrose, maltose, and lecithin are all considered legumes.

13. There is extensive debate among contemporary authorities regarding legumes that have been modified in form, such as sorbitol, dextrose not, ascorbic acid, citric acid, and aspirin.

A. It is permitted for a person to go out on Passover with matzah that was soaked. Likewise, Hatam Sofer wrote clearly that it is permissible, and the Pharisees are careful regarding soaking, lest some flour remain in the dough that did not bake well and thus fermented.

B. One who wishes to sanctify himself is permitted to refrain from eating soaked or cooked matzah, even if it is ground and kneaded, and he should not be forsaken. Those who are stringent should abstain from eating matzah crackers on Passover.

C. Our master Hafetz Hayim did not eat soaked matzah, but he allowed it for the members of his household.

D. Our master Rabbi Yaakov Yisroel Kanievsky covered the matzot throughout the holiday so that water would not come upon them.

E. There are those who are stringent not to eat matzah with anything else, and there are those who insist on cleaning the box from any dampness.

F. Roasted meat filled with matzah flour is considered soaked.

G. It seems that there is no need to be stringent not to dip baked matzah in water or a beverage if it is immediately placed into the mouth, as obviously there is no time for it to ferment at all, and certainly to dip it into wine, which is a fruit juice. In any case, our master Rabbi Shlomo Zalman instructed to hurry and eat immediately, so as not to give it time to ferment, and similarly, one who dips matzah in water should not let it sit for more than a minute. Rabbi Kanievsky was stringent for himself even with fruit juice. Even though he was lenient to say that there is no concern to eat matzah and drink water together since it is not soaked in the mouth, nevertheless, on the Seder night, he was stringent for himself even in this.

H. Those who are stringent regarding soaking do not use utensils that soaked matzah was eaten from, while others are not particular.

I. Some say there is no concern for soaking in butter and cheese.

J. There is a debate among the recent authorities if it is permissible to put matzah in the refrigerator so that it remains moist.

K. It is obvious that it is permissible to schedule a meal with one who ate soaked matzah.

L. Doubtfully soaked matzah is permissible for everyone.

M. It was customary to eat soaked matzah on the last day of the Diaspora. Some say it is to show that those who eat soaked matzah on Passover did not transgress any prohibition. Some say it is because of the joy of the holiday. And some say it is to unite with the entire people of Israel at the moment when it is possible.

N. Preparing soaked matzah for the last day of the Diaspora depends on customs.

O. A woman should act according to her husband's custom, whether stringent or lenient.

A. The Rambam writes: "Chametz on Pesach, even though it is a Torah prohibition, is not included in these [prohibitions of mixtures], because the mixture is never forbidden, since after Pesach the entire mixture will be permitted, as we have explained. Therefore, it is forbidden in any amount, whether in its own kind or not in its own kind."

This is puzzling, since we hold like Rabbi Shimon, who says that chametz after Pesach is forbidden by rabbinic decree. And it can be said that the Rambam holds that the prohibition of chametz after Pesach is a new prohibition, and the prohibition of Pesach has already been lifted.

B. The Rambam also writes: "One transgresses the prohibition of 'bal yira'ah and 'bal yimmatza' [on Pesach] regarding a mixture of chametz."

Some have interpreted this to mean that one only transgresses if there is enough chametz in the mixture for a kezayit (the minimum amount for eating). Others have interpreted it to mean that one transgresses even if there is not enough chametz in the mixture for a kezayit.

C. The Rambam also writes: "The Sages prohibited eating chametz from the beginning of the sixth hour in order that one not come to transgress a Torah prohibition. And from the beginning of the sixth hour, chametz is forbidden to be eaten or enjoyed for the entire sixth hour by rabbinic decree, and the rest of the day, from the seventh hour and onward, it is forbidden by the Torah. In the fifth hour, one may not eat chametz, as a precautionary measure against the possibility of a cloudy day, when one might be mistaken between the fifth and sixth hours."

The Gra"z explains that the prohibition of eating in the fifth hour is different from the prohibition of eating in the sixth hour. In the fifth hour, it is a prohibition of the object (chametz), while in the sixth hour, they made it like a Torah prohibition of the person (i.e., one is liable for lashes). Therefore, one is only liable for lashes from the sixth hour onward.

D. The Rambam also writes: "It is a positive commandment from the Torah to destroy chametz before the time of its prohibition to be eaten, as it is said (Shemot 12:15): 'On the first day you shall remove chametz from your homes.' And from the Oral Tradition we learned that this 'first' is the fourteenth day."

The Minchat Chinuch discusses at length whether the mitzvah of "tishbittu" (destroying chametz) is a negative commandment (i.e., not to have chametz in one's possession at the time of the prohibition) or a positive commandment. He concludes that Rashi and the Rambam hold that it is a negative commandment, and Rabbi Yehuda also holds this. The requirement to destroy chametz by burning does not stem from the mitzvah of tishbittu, but rather from the analogy to noteret (leftover sacrifices). The Tosafot hold that the mitzvah of tishbittu is a positive commandment for everyone. The Minchat Chinuch lists several practical differences between these two views.

The book מועדים וזמנים (Mo'adim u'Zmanim) argues that according to the Rambam, Rashi, and the Ran, there are two parts to the mitzvah of tishbittu. One is a negative commandment, that the chametz be removed from one's possession, and the other is a positive commandment, to destroy it through an act, as implied by the language of "tishbittu." The author adds that there are also two ways to nullify chametz. One is to nullify it in one's heart, in which case the chametz remains one's own but one no longer transgresses on it, and the other is to nullify it by saying "kol chamira," in which case it becomes ownerless and leaves one's possession entirely.

The Gra"ch argues that according to Rabbi Yehuda, who holds that the mitzvah of tishbittu is to burn chametz, the mitzvah is related to the object (chametz) and is a positive commandment. According to the Sages, who hold that the mitzvah of tishbittu can be fulfilled by any means, the mitzvah is primarily that the person (i.e., the Jew) not have chametz, and therefore it is dependent on a negative commandment.

The Avnei Nezer concludes that the mitzvah of tishbittu must be performed actively, and not just by not having chametz in one's possession.

The Chofetz Chaim innovates that the mitzvah of tishbittu includes two parts. The first is to remove the chametz from one's possession, in which case one no longer transgresses on the prohibitions of 'bal yira'ah' and 'bal yimmatza.' The second is to destroy it from the world, and the method of destruction is disputed between Rabbi Yehuda and the Sages.

The Peri Yitzchak writes that one who did not destroy chametz on the first day transgresses the verse "On the first day you shall remove chametz from your homes," but he still has the mitzvah of tishbittu all seven days of Pesach.

In the novelties of Rabbi Shmuel's interpretation, he raised the view of Maimonides, that as long as the obligation of nullifying [leaven] has not taken effect, one can give it to a non-Jew and be exempt from the mitzvah. However, from the moment the obligation of nullifying takes effect and onwards, the obligation of nullification has already taken effect upon him, and he must physically eliminate the leaven from the world, and giving it to a non-Jew will not help, whether according to the sages who hold that nullification applies to everything, or according to Rabbi Yehuda who holds that nullification is by burning.

In the book of Moedim and Zemanim, he raised the view of Maimonides, that a person who has leaven in his possession after the time of prohibition, violates "not seen" and "not found" once, not like the Tosafot who hold that he transgresses every moment that the leaven is in his possession. And in the novelties of Rabbi Shmuel, he raised that one transgresses the obligation of removing it from his possession every moment, but regarding the law of nullification that relates to the object, he does not transgress as long as the law of the object is ultimately fulfilled.

The Chazon Ish concludes, that by burning every olive-sized portion of leaven, one fulfills the obligation of nullification. And the opinion of the Or Sameach is that as long as one has an olive-sized portion of leaven, his obligation is not yet complete.

The Peni Yehoshua wrote, regarding an Israelite who entrusted his leaven to a non-Jew, if he violates "not seen" depends on the dispute of the Rishonim. The opinion of Rashi and the Ramban and some of the Geonim is that he does not violate "not seen." And the opinion of Maimonides and Rabbeinu Yonah is that he does violate, and the Rash explains their reasoning, that when the non-Jew designates a place for the Israelite's leaven, it implies that according to Rashi and his contemporaries, even if the non-Jew designates a place, he does not violate. And if a non-Jew entrusts his leaven to an Israelite, if he accepts responsibility, he violates according to the opinion of Rashi, even if he designates a house for him, and according to the opinion of the Tosafot, he does not violate if he designates a house for him.

In the book of Moedim and Zemanim, it is stated that one who does not have a house is not obligated in the mitzvah of nullifying leaven, and the implication is for children by their father who are not obligated in this mitzvah.

Regarding what the Shulchan Aruch wrote about checking the leaven, the Mishnah Berurah explained: "And one also needs to nullify the leaven at that time. And from the Torah, one of them is sufficient, for when one nullifies it in his heart and forsakes it, it is no longer his and he does not transgress. And certainly when he checks it, searches for it, and burns it from the world. However, our Sages were stringent that one is not sufficient but both are necessary, because they were concerned that since nullification depends on human thoughts and intentions, perhaps one might feel comfortable having leaven for several thousands [of currency], to abandon it, and even though he may say with his mouth that it will be null and ownerless and considered as dust, nevertheless, his heart does not think so, and he does not nullify it completely, and thus he transgresses "not seen", because he did not remove it from his house. Furthermore, since one is accustomed to it all year round, if it remains in his house and possession, we decree that he might forget and come to eat it. Therefore, our Sages ordained that even though one nullifies it, it is not sufficient, but he must check to burn it from the world. Nevertheless, one also needs to nullify it, lest he does not check properly and finds leaven on Passover and transgresses upon it."

Now, it is clear that one should not rely solely on selling the leaven without checking and nullifying it, because there is still concern that he might come to eat it, and even if nullification is added to the sale, it still does not serve from this reason. However, if one checks and sells without nullification, there is room to say that it is effective, since checking nullifies the concern of him eating it, and the sale nullifies the concern of transgressing "not seen", because it is no longer his. However, ideally, one should nullify it as per the enactment of our Sages, but if one forgets, he should not trouble his heart.

Regarding what the Mishnah Berurah wrote, that the reason for checking is that perhaps nullification will not be effective when he has leaven worth thousands, one needs to examine, in the case of one who only has crumbs of leaven worth a few cents, if nullification is sufficient for him, since he does not have the concern mentioned by the Mishnah Berurah, and also he will not come to eat these crumbs, and it is clear to him that he has no attractive piece in his house, or perhaps he still needs to nullify as per the enactment of our Sages. And there is another reason he will need to check as well, because on Passover, even a minute amount of leaven is prohibited, and it is not nullified even by a thousand, and if a crumb of leaven falls into his pot and he did not nullify it before the holiday, all his food will become prohibited.