Exodus 7:17; Exodus 7:19

17 This is what the LORD says: By this you will know that I am the LORD: With the staff that is in my hand I will strike the water of the Nile, and it will be changed into blood.

19 The LORD said to Moses, “Tell Aaron, ‘Take your staff and stretch out your hand over the waters of Egypt—over the streams and canals, over the ponds and all the reservoirs—and they will turn to blood.’ Blood will be everywhere in Egypt, even in vessels of wood and stone.”