Exodus 7:9 in the King James Version
When 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.
Context
8 The LORD spoke to Moses and to Aaron, saying,
9 “When Pharaoh speaks to you, saying, ‘Perform a miracle!’ then you shall tell Aaron, ‘Take your rod, and cast it down before Pharaoh, and it will become a serpent.’”
10 Moses and Aaron went in to Pharaoh, and they did so, as the LORD had commanded. Aaron cast down his rod before Pharaoh and before his servants, and it became a serpent.