Exodus 7:5-9

Then the Egyptians shall know that I am the Lord, when I extend My hand over Egypt and bring out the sons of Israel from their midst.”

So Moses and Aaron did this; as the Lord commanded them, so they did.

And Moses was eighty years old and Aaron eighty-three, when they spoke to Pharaoh. Aaron’s Staff Turns into a Serpent

Now the Lord spoke to Moses and Aaron, saying,

“When Pharaoh speaks to you, saying, ‘Work a miracle,’ then you shall say to Aaron, ‘Take your staff and throw it down before Pharaoh, so that it may turn into a serpent.’ ”