Exodus 7:1

I have made thee a god to Pharaoh — That is, my representative in this affair, as magistrates are called gods, because they are God's vicegerents. He was authorized to speak and act in God's name, and endued with a divine power, to do that which is above the ordinary course of nature. And Aaron shall be thy prophet — That is, he shall speak from thee to Pharaoh, as prophets do from God to the children of men. Thou shalt as a god inflict and remove the plagues, and Aaron as a prophet shall denounce them.