Exodus 7:8-10

Living Bible

⁸ Then the Lord said to Moses and Aaron, ⁹ “Pharaoh will demand that you show him a miracle to prove that God has sent you; when he does, Aaron is to throw down his rod, and it will become a serpent.”

¹⁰ So Moses and Aaron went in to see Pharaoh, and performed the miracle, as Jehovah had instructed them—Aaron threw down his rod before Pharaoh and his court, and it became a serpent.