Exodus 7:1-9

Then the LORD said to Moses, “See, I make you as God to Pharaoh, and your brother Aaron shall be your prophet. You shall speak all that I command you, and your brother Aaron shall speak to Pharaoh that he let the sons of Israel go out of his land. But I will harden Pharaoh’s heart that I may multiply My signs and My wonders in the land of Egypt. When Pharaoh does not listen to you, then I will lay My hand on Egypt and bring out My hosts, My people the sons of Israel, from the land of Egypt by great judgments. The Egyptians shall know that I am the LORD, when I stretch out My hand on Egypt and bring out the sons of Israel from their midst.” So Moses and Aaron did it; as the LORD commanded them, thus they did. Moses was eighty years old and Aaron eighty-three, when they spoke to Pharaoh. Now the LORD spoke to Moses and Aaron, saying, “When Pharaoh speaks to you, saying, ‘Work a miracle,’ then you shall say to Aaron, ‘Take your staff and throw it down before Pharaoh, that it may become a serpent.’ ”