Exodus 7:19-20

And the LORD said to Moses, “Say to Aaron, ‘Take your staff and stretch out your hand over the waters of Egypt, over their rivers, their canals, and their ponds, and all their pools of water, so that they may become blood, and there shall be blood throughout all the land of Egypt, even in vessels of wood and in vessels of stone.’” Moses and Aaron did as the LORD commanded. In the sight of Pharaoh and in the sight of his servants he lifted up the staff and struck the water in the Nile, and all the water in the Nile turned into blood.