Exodus 7:13

9“When Pharaoh speaks to you, saying, ‘Perform a miracle!’ then you shall tell Aaron, ‘Take your rod, and cast it down before Pharaoh, and it will become a serpent.’”

10Moses and Aaron went in to Pharaoh, and they did so, as the LORD had commanded. Aaron cast down his rod before Pharaoh and before his servants, and it became a serpent.

11Then Pharaoh also called for the wise men and the sorcerers. They also, the magicians of Egypt, did the same thing with their enchantments.

12For they each cast down their rods, and they became serpents; but Aaron’s rod swallowed up their rods.

13Pharaoh’s heart was hardened, and he didn’t listen to them, as the LORD had spoken.

14The LORD said to Moses, “Pharaoh’s heart is stubborn. He refuses to let the people go.

15Go to Pharaoh in the morning. Behold, he is going out to the water. You shall stand by the river’s bank to meet him. You shall take the rod which was turned to a serpent in your hand.

16You shall tell him, ‘The LORD, the God of the Hebrews, has sent me to you, saying, “Let my people go, that they may serve me in the wilderness. Behold, until now you haven’t listened.”

17The LORD says, “In this you shall know that I am the LORD. 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.