Exodus 7:21-22

7:21 When the fish that were in the Nile died, the Nile began to stink, so that the Egyptians could not drink water from the Nile. There was blood everywhere in the land of Egypt! 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.