(Read Exodus 6:14-30)
Moses and Aaron were Israelites; raised up unto them of their brethren, as Christ also should be, who was to be the Prophet and Priest, the Redeemer and Lawgiver of the people of Israel. Moses returns to his narrative, and repeats the charge God had given him to deliver his message to Pharaoh, and his objection against it. Those who have spoken unadvisedly with their lips ought to reflect upon it with regret, as Moses seems to do here. “Uncircumcised,” is used in Scripture to note the unsuitableness there may be in any thing to answer its proper purpose; as the carnal heart and depraved nature of fallen man are wholly unsuited to the services of God, and to the purposes of his glory. It is profitable to place no confidence in ourselves, all our sufficiency must be in the Lord. We never can trust ourselves too little, or our God too much. I can do nothing by myself, said the apostle, but I can do all things through Christ which strengtheneth me.
For a more detailed summary select the link below.
Exodus 6 Bible Commentary – Matthew Henry (concise) (christianity.com)
30 Moses said before Yahweh, “Behold, I am of uncircumcised lips, and how shall Pharaoh listen to me?”