Exodus 7:11-15

Then Pharaoh also called the wise men and the sorcerers: now the magicians of Egypt, they also did in like manner with their enchantments.

For they cast down every man his rod, and they became serpents: but Aaron’s rod swallowed up their rods.

And he hardened Pharaoh’s heart, that he hearkened not unto them; as the LORD had said.

And the LORD said unto Moses, Pharaoh’s heart is hardened, he refuseth to let the people go.

Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river’s brink against he come; and the rod which was turned to a serpent shalt thou take in thine hand.