Exodus 7:8 KJV

6And Moses and Aaron did as the LORD commanded them, so did they.

7And Moses was fourscore years old, and Aaron fourscore and three years old, when they spake unto Pharaoh.

8And the LORD spake unto Moses and unto Aaron, saying,

9When Pharaoh shall speak unto you, saying, Shew a miracle for you: then thou shalt say unto Aaron, Take thy rod, and cast it before Pharaoh, and it shall become a serpent.

10And Moses and Aaron went in unto Pharaoh, and they did so as the LORD had commanded: and Aaron cast down his rod before Pharaoh, and before his servants, and it became a serpent.