Exodus 7:8-13 NLT

8 Then the LORD said to Moses and Aaron,
9 "Pharaoh will demand that you show him a miracle to prove that God has sent you. When he makes this demand, say to Aaron, 'Throw down your shepherd's staff,' and it will become a snake."
10 So Moses and Aaron went to see Pharaoh, and they performed the miracle just as the LORD had told them. Aaron threw down his staff before Pharaoh and his court, and it became a snake.
11 Then Pharaoh called in his wise men and magicians, and they did the same thing with their secret arts.
12 Their staffs became snakes, too! But then Aaron's snake swallowed up their snakes.
13 Pharaoh's heart, however, remained hard and stubborn. He still refused to listen, just as the LORD had predicted.