Exodus 7:7-9

Young's Literal Translation

⁷ and Moses [is] a son of eighty years, and Aaron [is] a son of eighty and three years, in their speaking unto Pharaoh.

⁸ And Jehovah speaketh unto Moses and unto Aaron, saying,

⁹ `When Pharaoh speaketh unto you, saying, Give for yourselves a wonder; then thou hast said unto Aaron, Take thy rod, and cast before Pharaoh -- it becometh a monster.'