And still need clarification on Rashi's method, who explained that "Shabbatah" is the nullification of leaven, for apparently the meaning of "Shabbatah" is to completely eliminate from the world, and why is the nullification called "Shabbatah," after all, the leaven is still before us, and what is ceased in it.

Indeed, the Ramban wrote in explaining Rashi's method: "It is possible and correct to say according to the words of Rashi that we derive this from the Midrash Tashbitu, for this is what the Merciful One said: 'You shall cease [tashbitu] it from leaven,' and it should not appear as leaven before you, but rather as if it were burned, and you should see it as dust and ashes and not want its existence, for it is not written 'You shall burn it or destroy it,' as it is written regarding other prohibitions, as explained in Avodah Zarah (Sanhedrin 55a), 'destroy and burn and annihilate.' Nevertheless, nullification is its name, that one nullifies in his heart the law of leaven and does not desire its existence, and this is the meaning of "Shabbatah" everywhere, like the concept of 'You shall not cease [tashbit] the salt of your God' (Leviticus 2:13), do not nullify. And so too the meaning of Shabbatah, the nullification of work, and likewise Onkelos translates, 'You shall nullify the leaven.' And this is what they said in the Gemara (Yoma 10a) explicitly, 'Is the search for leaven biblical? It is rabbinic, for with biblical nullification alone it suffices for him,' and they do not bring a verse, for it is understood from the verse that nullification is the main thing."

In other words, the "Shabbatah" is accomplished through nullifying its significance, as in the eyes of a person, the leaven has lost all its value, and he does not desire its existence, therefore it is nullified from the law of leaven. These matters still require definition and explanation.