Exodus 7:17-20

17Thus saith Jehovah: In this shalt thou know that I am Jehovah — behold, I will smite with the staff that is in my hand upon the water which is in the river, and it shall be turned into blood.

18And the fish that is in the river shall die; and the river shall stink; and the Egyptians shall loathe to drink the water out of the river.

19And Jehovah said to Moses, Say unto Aaron, Take thy staff, and stretch out thy hand upon the waters of the Egyptians — upon their streams, upon their rivers, and upon their ponds, and upon all their reservoirs of water, that they may become blood; and there shall be blood throughout the land of Egypt, both in [vessels of] wood and in [vessels of] stone.

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.