Exodus 7:1-9

And Jehovah said unto Moses, See, I have made thee as God to Pharaoh; and Aaron thy brother shall be thy prophet. Thou shalt speak all that I command thee; and Aaron thy brother shall speak unto Pharaoh, that he let the children of Israel go out of his land. And I will harden Pharaoh’s heart, and multiply my signs and my wonders in the land of Egypt. But Pharaoh will not hearken unto you, and I will lay my hand upon Egypt, and bring forth my hosts, my people the children of Israel, out of the land of Egypt by great judgments. And the Egyptians shall know that I am Jehovah, when I stretch forth my hand upon Egypt, and bring out the children of Israel from among them. And Moses and Aaron did so; as Jehovah commanded them, so did they. And Moses was fourscore years old, and Aaron fourscore and three years old, when they spake unto Pharaoh. And Jehovah spake unto Moses and unto Aaron, saying, When Pharaoh shall speak unto you, saying, Show a wonder for you; then thou shalt say unto Aaron, Take thy rod, and cast it down before Pharaoh, that it become a serpent.