Behold, in the words of Rabbi Yosef Bechor Shor, the third of the four questions with which we began our discussion is also resolved. The Torah appropriately delayed the description of the prevention of drinking from the waters of the Nile—"and the Egyptians could not drink water from the Nile"—to verse 21, after describing the death of the fish in the Nile. This is because the death of the fish and the stench of their carcasses rendered the water undrinkable. Had the fish not died, there would have been no prevention in drinking from the waters of the Nile once they reverted to their original state.

Furthermore, it is also explained according to his words— as he noted in his commentary—why Pharaoh did not ask Moses and Aaron to remove the plague and restore the water to its original state. On the contrary, he dismissed the matter indifferently, as it is said: "Pharaoh turned and went into his house, and he did not take this to heart." This was because the water had already returned to its original state shortly after it turned to blood.

Additionally, according to his explanation, the fourth question we posed is resolved. How can it be said "and the Egyptians could not drink water from the Nile," when there was no water in it, only blood? According to his explanation, it is well understood, as it was only temporarily blood, and afterward, it returned to its original state. And during that time when the Nile returned to its original state, it is said that the water was nonetheless foul due to the stench of the dead fish, and the Egyptians could not drink from it.

It is worth noting that this question is also answered according to what I found in the Torah commentaries of the Tosafists (Tosafot HaShalem Gliss, verse 24, letter dalet), who wrote that the Egyptians dug around the Nile because its waters, the waters of the Nile, were blessed. Therefore, it can be said that this is why the scripture added the words 'water from the Nile,' to emphasize the great calamity that struck Egypt with this plague. They were not merely afflicted by the prevention of drinking water, as would be implied if it said 'and the Egyptians could not drink,' as per our question, but more significantly—they were accustomed to drinking 'blessed' water, the waters of the Nile, and now this goodness was taken from them.

Returning to the words of Rabbi Yosef Bechor Shor: another issue clarified by his explanation is the digging around the Nile, as it is said: "And all the Egyptians dug around the Nile for water to drink because they could not drink from the waters of the Nile." On the surface, this is difficult to understand—what benefit was there in this digging, since even those waters turned to blood? Some have explained [Shivtei Zekenim and Chizkuni] that the plague affected only the surface waters, not the underground waters. Indeed, according to Rabbi Yosef Bechor Shor's explanation, it is well understood, as brought in the Torah commentaries of the Tosafists (Tosafot HaShalem Gliss, verse 24, letter aleph), since according to his words, the waters returned to their original state shortly after being struck, and the prevention of drinking from the Nile's waters was due to the stench of the dead fish. Therefore, digging would indeed be an effective remedy, as they would find springs without fish, and in the absence of fish, there would be no stench, and from there, they could drink and be satisfied.

In any case, we have two approaches regarding the duration of the blood in the land of Egypt: the opinion of Rabbi Yosef Bechor Shor is that it was for a short time, and immediately afterward, the waters returned to their original state. Whereas Rashbam (brought in Tosafot HaShalem Gliss, verse 18, letter zayin) and most of the early commentators held that the blood lasted for seven days.