Exodus 6:10-13

Then GOD said to Moses, “Go and speak to Pharaoh king of Egypt so that he will release the Israelites from his land.” Moses answered GOD, “Look—the Israelites won’t even listen to me. How do you expect Pharaoh to? And besides, I stutter.” But GOD again laid out the facts to Moses and Aaron regarding the Israelites and Pharaoh king of Egypt, and he again commanded them to lead the Israelites out of the land of Egypt.