Exodus 7:1-3

And the LORD said unto Moses, See, I have made thee a 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 send the children of Israel out of his land. And I will harden Pharaoh's heart, and multiply my signs and my wonders in the land of Egypt.