Exodus 7:20-22

20Moses and Aaron did just as the Lord had commanded; in the sight of Pharaoh and his officials, he raised the staff and struck the water in the Nile, and all the water in the Nile was turned to blood.

21The fish in the Nile died, and the river smelled so bad the Egyptians could not drink water from it. There was blood throughout the land of Egypt.

22But the magicians of Egypt did the same thing by their occult practices. So Pharaoh’s heart was hard, and he would not listen to them, as the Lord had said.