Exodus 7:22-25

22But the magicians of Egypt did the same with their secret arts. So Pharaoh’s heart was hardened, and he did not listen to them—just as Adonai had said.

23Pharaoh turned and went into his house, and did not even take it to heart.

24So all the Egyptians dug around the river for water to drink, because they could not drink of the water from the Nile.

25Seven days were fulfilled after Adonai had struck the Nile.