Exodus 6:12 - Coke's Commentary on the Holy Bible

Moses spake before the Lord— The phrase before the Lord, evidently denotes some visible appearance of the Deity, that divine Shechinah, in which God discovered himself to Moses. Uncircumcised lips, according to the meaning of the phrase in other parts of Scripture, expresses vile, unworthy, unfit; and therefore Moses here, with great modesty and humility, declares his own unworthiness and inability to persuade Pharaoh. The expression seems similar in import to that which he uses, ch. Exodus 4:10 though, perhaps, it is more emphatically lowly. It is very certain, that the word uncircumcised, was used as a term of contempt among the Jews; who used to call the Gentiles uncircumcised. Hence they speak of uncircumcised ears; uncircumcised hearts; Jeremiah 6:10; Jeremiah 9:26 which imply hearts and ears unholy and unsanctified; deaf to true wisdom; insensible of true goodness; vile and unworthy. To suppose, as some have done from this passage, that Moses was tongue-tied, seems ridiculous enough. The phrase, naturally and clearly expresses his lowly opinion of himself, his unfitness for such an office, and his inability to persuade or prevail.