Exodus 7:7

⁵  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.

⁶  And Moses and Aaron did as the LORD commanded them, so did they.

⁷  And Moses was fourscore years old, and Aaron fourscore and three years old, when they spake unto Pharaoh.

⁸  And the LORD spake unto Moses and unto Aaron, saying,

⁹  When Pharaoh shall speak unto you, saying, Show a miracle for you: then thou shalt say unto Aaron, Take thy rod, and cast it before Pharaoh, and it shall become a serpent.