Moses replied, “Look, I have uncircumcised lips, and how will Pharaoh listen to me?” (Ex. 6:30).
In the end, God appointed Aaron as the spokesman (the translations sometimes say, “Aaron your brother will be your prophet”, but, as the commentators point out, the Hebrew navi does not mean prophet in the normal sense, but interpreter or spokesman).
The issue on which this note focusses, however, is that of Moses calling himself a man of uncircumcised lips.
The Hebrew aral s’fatayim is a quite common idiom. It denotes a person with a speech defect. The imagery is found in other contexts also, e.g. aral levav – uncircumcised of heart (Deut. 10:16). The nations are deemed arelim, spiritually and morally uncircumcised (Jer. 9:25). Judah and Jerusalem are told by God, “Circumcise yourselves to the Lord, and take away the foreskins of your heart” (Jer. 4:4) – i.e. remove whatever is obstructing you from heeding the Divine will.
It is obvious where the circumcision imagery originates, but the important thing is that if some factor or influence is preventing us from being as God wants us, we must take action to do what needs to be done.