Exodus 7:8

5 And the Egyptians will see that I am the Lord, when my hand is stretched out over Egypt, and I take the children of Israel out from among them.

6 And Moses and Aaron did so: as the Lord gave them orders, so they did.

7 And Moses was eighty years old, and Aaron eighty-three years old, when they gave the Lord's word to Pharaoh.

9 If Pharaoh says to you, Let me see a wonder: then say to Aaron, Take your rod and put it down on the earth before Pharaoh so that it may become a snake.

10 Then Moses and Aaron went in to Pharaoh and they did as the Lord had said: and Aaron put his rod down on the earth before Pharaoh and his servants, and it became a snake.

11 Then Pharaoh sent for the wise men and the wonder-workers, and they, the wonder-workers of Egypt, did the same with their secret arts.