“The fish that are in the Nile will die and the Nile will become foul; and the Egyptians will loathe to drink water from the Nile. The Lord said to Moses: Say to Aaron: Take your staff, and stretch your hand over the water of Egypt, over their rivers, over their streams, and over their ponds, and over all their pools of water, and they will become blood; and there will be blood throughout the entire land of Egypt, and in the wood and in the stone vessels” (Exodus 7:18–19).
“The fish that are in the Nile will die.… The Lord said to Moses: Say to Aaron.” Rabbi Tanḥum said: Why was the water not afflicted by Moses? The Holy One blessed be He said to him: ‘The water that protected you when you were cast into the Nile, it is not appropriate for it to be afflicted by you. By your life, it will be afflicted only by Aaron.’
“Stretch your hand over the water of Egypt” – everything that was in the Nile, in the ponds, and in the rivers; “and over all their pools of water, and they will become blood” – [including water] that was in a jug; “and there will be blood throughout the entire land of Egypt” – even what an Egyptian spit was blood. Why did the Holy One blessed be He bring blood upon them? It was measure for measure,14A punishment that fit the crime. as He said to Abraham: “The nation that they will serve I will judge…” (Genesis 15:14).
It is because they did not allow Israelite women to immerse from their impurity, so they would not procreate; therefore, the water was afflicted with blood.15It is because they prevented the Israelite women from immersing to purify themselves from their menstrual blood. Consequently, it was prohibited for them to cohabit with their husbands. “Moses and Aaron did so, as the Lord commanded; and he lifted the rod, and struck the water that was in the Nile, before the eyes of Pharaoh, and before the eyes of his servants; and all the water that was in the Nile turned into blood.
The fish that were in the Nile died; and the Nile became foul, and the Egyptians could not drink water from the Nile; and the blood was throughout the land of Egypt” (Exodus 7:20–21). “Moses and Aaron did so, as the Lord commanded.… The fish that were in the Nile died” – Rabbi Avin HaLevi, son of Rabbi, said: Israel became wealthy from the plague of blood. How so? If an Egyptian and an Israelite were in one house and the tub was full of water, and the Egyptian went to fill the jug from it, he would remove it filled with blood, but the Israelite would drink water from the tub.
The Egyptian would say: ‘Give me a little water with your hand.’ He would give it to him, and it would become blood. He would say to him: ‘Let you and I drink water from one bowl,’ and the Israelite would drink water and the Egyptian blood. But when he would purchase it from the Israelite with money, he would drink water. From this, Israel became wealthy.