Exodus 7:10 (KJV)

And the Egyptians shall know that I am the LORD, when I stretch forth mine hand upon Egypt, and bring out the children of Israel from among them.

And Moses and Aaron did as the LORD commanded them, so did they.

And Moses was fourscore years old, and Aaron fourscore and three years old, when they spake unto Pharaoh.

And the LORD spake unto Moses and unto Aaron, saying,

When Pharaoh shall speak unto you, saying, Shew a miracle for you: then thou shalt say unto Aaron, Take thy rod, and cast it before Pharaoh, and it shall become a serpent.

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

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

And he hardened Pharaoh's heart, that he hearkened not unto them; as the LORD had said.

And the LORD said unto Moses, Pharaoh's heart is hardened, he refuseth to let the people go.

Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river's brink against he come; and the rod which was turned to a serpent shalt thou take in thine hand.