Exodus 7:8-14 NIV
The LORD said to Moses and Aaron, “When Pharaoh says to you, ‘Perform a miracle,’ then say to Aaron, ‘Take your staff and throw it down before Pharaoh,’ and it will become a snake.”
So Moses and Aaron went to Pharaoh and did just as the LORD commanded. Aaron threw his staff down in front of Pharaoh and his officials, and it became a snake. Pharaoh then summoned wise men and sorcerers, and the Egyptian magicians also did the same things by their secret arts: Each one threw down his staff and it became a snake. But Aaron’s staff swallowed up their staffs. Yet Pharaoh’s heart became hard and he would not listen to them, just as the LORD had said.
Then the LORD said to Moses, “Pharaoh’s heart is unyielding; he refuses to let the people go.
NIV: New International Version