Exodus 7:20-25

20And Moses and Aaron did so, as Jehovah had commanded; and he lifted up the staff, and smote the waters that were in the river before the eyes of Pharaoh, and before the eyes of his bondmen; and all the waters that were in the river were turned into blood. 21And the fish that was in the river died; and the river stank, and the Egyptians could not drink the water of the river; and the blood was throughout the land of Egypt. 22And the scribes of Egypt did so with their sorceries; and Pharaoh's heart was stubborn, neither did he hearken to them, as Jehovah had said. 23And Pharaoh turned and went into his house, and took not this to heart either. 24And all the Egyptians dug round about the river for water to drink; for they could not drink of the water of the river. 25And seven days were fulfilled, after Jehovah had smitten the river.