John Calvin's Commentary on the Bible - Exodus 6:9
Verse 9 9.And Moses spake so. From this verse it appears that Moses is referring to the second message which he was commanded to bear. For they had before heard with great joy and approbation, and had expressed their thankfulness to God, that the time of their deliverance was come. Now Moses relates that their hearts were shut against the announcement that he made to them of this grace. Thus do the afflicted often, by closing their ears, shut the gate against the promises of God, which is... read more
Adam Clarke's Commentary on the Bible - Exodus 6:12
Uncircumcised lips? - The word ערל aral , which we translate uncircumcised, seems to signify any thing exuberant or superfluous. Had not Moses been remarkable for his excellent beauty, I should have thought the passage might be rendered protuberant lips; but as this sense cannot be admitted for the above reason, the word must refer to some natural impediment in his speech; and probably means a want of distinct and ready utterance, either occasioned by some defect in the organs of speech,... read more