Exodus 7:6

2 You are to speak all that I command you, and your brother Aaron is to tell Pharaoh to let the Israelites go out of his land.

3 But I will harden Pharaoh’s heart, and though I will multiply My signs and wonders in the land of Egypt,

4 Pharaoh will not listen to you. Then I will lay My hand on Egypt, and by mighty acts of judgment I will bring the divisions of My people the Israelites out of the land of Egypt.

5 And the Egyptians will know that I am the LORD, when I stretch out My hand against Egypt and bring the Israelites out from among them.”

6 So Moses and Aaron did just as the LORD had commanded them.

7 Moses was eighty years old and Aaron was eighty-three when they spoke to Pharaoh.

8 The LORD said to Moses and Aaron,

9 “When Pharaoh tells you, ‘Perform a miracle,’ you are to say to Aaron, ‘Take your staff and throw it down before Pharaoh,’ and it will become a serpent.”

10 So Moses and Aaron went to Pharaoh and did just as the LORD had commanded. Aaron threw his staff down before Pharaoh and his officials, and it became a serpent.

Read all of Exodus 7