Exodus 7:8-13

8Then the Lord said to Moses and Aaron,

9"When Pharaoh says to you, 'Prove yourselves by working a miracle,' then you shall say to Aaron, 'Take your staff and cast it down before Pharaoh, that it may become a serpent.'"

10So Moses and Aaron went to Pharaoh and did just as the Lord commanded. Aaron cast down his staff before Pharaoh and his servants, and it became a serpent.

11Then Pharaoh summoned the wise men and the sorcerers, and they, the magicians of Egypt, also did the same by their secret arts.

12For each man cast down his staff, and they became serpents. But Aaron's staff swallowed up their staffs.

13Still Pharaoh's heart was hardened, and he would not listen to them, as the Lord had said.