Exodus 7:22-25

7:22 But the magicians of Egypt did the same by their secret arts, and so Pharaoh’s heart remained hard, and he refused to listen to Moses and Aaron – just as the Lord had predicted. 7:23 And Pharaoh turned and went into his house. He did not pay any attention to this. 7:24 All the Egyptians dug around the Nile for water to drink, because they could not drink the water of the Nile.

The Second Blow: Frogs

7:25 Seven full days passed after the Lord struck the Nile.