Exodus 7:2-5

Tell Aaron your brother everything that I command you, and let him tell the king of Egypt to let the Israelites leave his country. But I will make the king stubborn. I will do many miracles in Egypt, but he will still refuse to listen. So then I will punish Egypt terribly, and I will lead my divisions, my people the Israelites, out of that land. I will punish Egypt with my power, and I will bring the Israelites out of that land. Then they will know I am the LORD.”