Exodus 7:11

8 And Jehovah spake unto Moses and unto Aaron, saying,

9 When Pharaoh shall speak unto you, saying, Show a wonder for you; then thou shalt say unto Aaron, Take thy rod, and cast it down before Pharaoh, that it become a serpent.

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

11 Then Pharaoh also called for the wise men and the sorcerers: and they also, the magicians of Egypt, did in like manner with their enchantments.

12 For they cast down every man his rod, and they became serpents: but Aaron`s rod swallowed up their rods.

13 And Pharaoh`s heart was hardened, and he hearkened not unto them; as Jehovah had spoken.

14 And Jehovah said unto Moses, Pharaoh`s heart is stubborn, he refuseth to let the people go.