Cross reference
Exodus 6:30
30 Moses said before Yahweh, "Behold, I am of uncircumcised lips, and how shall Pharaoh listen to me?"
Exodus 6:12
12 Moses spoke before Yahweh, saying, "Behold, the children of Israel haven't listened to me. How then shall Pharaoh listen to me, who am of uncircumcised lips?"
Exodus 4:10
10 Moses said to Yahweh, "Oh, Lord, I am not eloquent, neither before now, nor since you have spoken to your servant; for I am slow of speech, and of a slow tongue."
1 Corinthians 9:16-17
16 For if I preach the Gospel, I have nothing to boast about; for necessity is laid on me; but woe is to me, if I don't preach the Gospel.
17 For if I do this of my own will, I have a reward. But if not of my own will, I have a stewardship entrusted to me.