Exodus 6:10-13

So the LORD said to Moses, “Go in, tell Pharaoh king of Egypt to let the people of Israel go out of his land.” But Moses said to the LORD, “Behold, the people of Israel have not listened to me. How then shall Pharaoh listen to me, for I am of uncircumcised lips?” But the LORD spoke to Moses and Aaron and gave them a charge about the people of Israel and about Pharaoh king of Egypt: to bring the people of Israel out of the land of Egypt.