Exodus 6:28-30

And it came to pass on the day when Jehovah spake unto Moses in the land of Egypt, that Jehovah spake unto Moses, saying, I am Jehovah: speak thou unto Pharaoh king of Egypt all that I speak unto thee. And Moses said before Jehovah, Behold, I am of uncircumcised lips, and how shall Pharaoh hearken unto me?