Exodus 6:30

²⁸  And it came to pass on the day when the LORD spake unto Moses in the land of Egypt,

²⁹  That the LORD spake unto Moses, saying, I am the LORD: speak thou unto Pharaoh king of Egypt all that I say unto thee.

³⁰  And Moses said before the LORD, Behold, I am of uncircumcised lips, and how shall Pharaoh hearken unto me?