'Uncircumcised Lips' in the Bible

And Moses spake before Yahweh, saying, - Lo! the sons of Israel have not hearkened unto me, how then shall Pharaoh, hear, I, also being of uncircumcised lips.

And Moses said before Yahweh, - Lo! I, am of uncircumcised lips, how then will Pharaoh hearken unto me?