Exodus 7:10

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

8 And the Lord said to Moses and Aaron,

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.

12 For every one of them put down his rod on the earth, and they became snakes: but Aaron's rod made a meal of their rods.

13 But Pharaoh's heart was made hard, and he did not give ear to them, as the Lord had said.