Exodus 7:7 WEB

⁵  The Egyptians shall know that I am Yahweh, when I stretch forth my hand on Egypt, and bring out the children of Israel from among them.'

⁶  Moses and Aaron did so. As Yahweh commanded them, so they did.

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

⁸  Yahweh spoke to Moses and to Aaron, saying,

⁹  'When Pharaoh speaks to you, saying, 'Perform a miracle!' then you shall tell Aaron, 'Take your rod, and cast it down before Pharaoh, that it become a serpent.''