Exodus 6:10-13

And the LORD spoke to Moses, saying, “Go in, tell Pharaoh king of Egypt to let the children of Israel go out of his land.” And Moses spoke before the LORD, saying, “The children of Israel have not heeded me. How then shall Pharaoh heed me, for I am of uncircumcised lips?” Then the LORD spoke to Moses and Aaron, and gave them a command for the children of Israel and for Pharaoh king of Egypt, to bring the children of Israel out of the land of Egypt.