Exodus 7
15 Ref Go to Pharaoh in the morning. Behold, he goes out to the water; and you shall stand by the river's bank to meet him; and the rod which was turned to a serpent you shall take in your hand.
16 Ref You shall tell him, 'Yahweh, the God of the Hebrews, has sent me to you, saying, "Let my people go, that they may serve me in the wilderness:" and, behold, until now you haven't listened.
17 Ref Thus says Yahweh, "In this you shall know that I am Yahweh. Behold, I will strike with the rod that is in my hand on the waters which are in the river, and they shall be turned to blood.
18 Ref The fish that are in the river shall die, and the river shall become foul; and the Egyptians shall loathe to drink water from the river."'"