Exodus 7:14

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

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

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

Go 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.

You 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.”

The 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.