Shemot 7:7-9

Orthodox Jewish Bible

⁷ And Moshe was fourscore years old, and Aharon fourscore three years, when they spoke unto Pharaoh.

⁸ And Hashem spoke unto Moshe and Aharon, saying,

⁹ When Pharaoh shall speak unto you, saying, Show a mofet (miracle) for you: then thou shalt say unto Aharon, Take thy matteh, and cast it before Pharaoh, and it shall become a serpent.