Exodus 7
19 Ref And the Lord said, Say to Aaron, Let the rod in your hand be stretched out over the waters of Egypt, and over the rivers and the streams and the pools, and over every stretch of water, so that they may be turned to blood; and there will be blood through all the land of Egypt, in vessels of wood and in vessels of stone.
20 Ref And Moses and Aaron did as the Lord had said; and when his rod had been lifted up and stretched out over the waters of the Nile before the eyes of Pharaoh and his servants, all the water in the Nile was turned to blood;