Exodus 6:12

6:12 And Moses spake before the LORD, saying, Behold, the children of Israel have not hearkened unto me; how then shall Pharaoh hear me, who [am] of uncircumcised lips?

Jeremiah 1:6

1:6 Then said I, Ah, Lord GOD! behold, I cannot speak: for I [am] a child.

Acts 7:22

7:22 And Moses was learned in all the wisdom of the Egyptians, and was mighty in words and in deeds.