EXO 7:20

20 And Moses and Aaron did so, as the Lord commanded; and Aaron raised the rod, and smote the water of the flood before Pharaoh and his servants, which water was turned into blood; (And Moses and Aaron did as the Lord commanded; and Aaron raised up his staff, and struck the water of the (Nile) River before Pharaoh and his servants, and the water was turned into blood;)