Exodus 7:15-18

15Go to Pharaoh in the morning when he goes out to the water. Position yourself to meet him by the edge of the Nile, and take in your hand the staff that was turned into a snake.

16Tell him, ‘The Lord, the God of the Hebrews, has sent me to you to say, “Release my people, that they may serve me in the desert!” But until now you have not listened.

17Thus says the Lord: “By this you will know that I am the Lord: I am going to strike the water of the Nile with the staff that is in my hand, and it will be turned into blood.

18Fish in the Nile will die, the Nile will stink, and the Egyptians will be unable to drink water from the Nile.”’”