Exodus 9:13-14

Then the LORD said to Moses, “Get up early in the morning and stand before Pharaoh. Tell him, ‘This is what the LORD, the God of the Hebrews, says: Let my people go, so they can worship me. If you don’t, I will send more plagues on you and your officials and your people. Then you will know that there is no one like me in all the earth.