A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
exo 6:1RENEWAL OF THE PROMISE. (Exo 6:1-13)
the Lord said unto Moses--The Lord, who is long-suffering and indulgent to the errors and infirmities of His people, made allowance for the mortification of Moses as the result of this first interview and cheered him with the assurance of a speedy and successful termination to his embassy.
exo 6:2And God spake unto Moses--For his further encouragement, there was made to him an emphatic repetition of the promise (Exo 3:20).
exo 6:3I . . . God Almighty--All enemies must fall, all difficulties must vanish before My omnipotent power, and the patriarchs had abundant proofs of this.
but by my name, &c.--rather, interrogatively, by My name Jehovah was I not known to them? Am not I, the Almighty God, who pledged My honor for the fulfilment of the covenant, also the self-existent God who lives to accomplish it? Rest assured, therefore, that I shall bring it to pass. This passage has occasioned much discussion; and it has been thought by many to intimate that as the name Jehovah was not known to the patriarchs, at least in the full bearing or practical experience of it, the honor of the disclosure was reserved to Moses, who was the first sent with a message in the name of Jehovah, and enabled to attest it by a series of public miracles.
exo 6:9Moses spake so unto the children of Israel--The increased severities inflicted on the Israelites seem to have so entirely crushed their spirits, as well as irritated them, that they refused to listen to any more communications (Exo 14:12). Even the faith of Moses himself was faltering; and he would have abandoned the enterprise in despair had he not received a positive command from God to revisit the people without delay, and at the same time renew their demand on the king in a more decisive and peremptory tone.
exo 6:12how then shall . . . who am of uncircumcised lips?--A metaphorical expression among the Hebrews, who, taught to look on the circumcision of any part as denoting perfection, signified its deficiency or unsuitableness by uncircumcision. The words here express how painfully Moses felt his want of utterance or persuasive oratory. He seems to have fallen into the same deep despondency as his brethren, and to be shrinking with nervous timidity from a difficult, if not desperate, cause. If he had succeeded so ill with the people, whose dearest interests were all involved, what better hope could he entertain of his making more impression on the heart of a king elated with pride and strong in the possession of absolute power? How strikingly was the indulgent forbearance of God displayed towards His people amid all their backwardness to hail His announcement of approaching deliverance! No perverse complaints or careless indifference on their part retarded the development of His gracious purposes. On the contrary, here, as generally, the course of His providence is slow in the infliction of judgments, while it moves more quickly, as it were, when misery is to be relieved or benefits conferred.
exo 6:14THE GENEALOGY OF MOSES. (Exo. 6:14-30)
These be the heads of their fathers' houses--chiefs or governors of their houses. The insertion of this genealogical table in this part of the narrative was intended to authenticate the descent of Moses and Aaron. Both of them were commissioned to act so important a part in the events transacted in the court of Egypt and afterwards elevated to so high offices in the government and Church of God, that it was of the utmost importance that their lineage should be accurately traced. Reuben and Simeon being the oldest of Jacob's sons, a passing notice is taken of them, and then the historian advances to the enumeration of the principal persons in the house of Levi [Exo 6:16-19].
exo 6:20Amram took him Jochebed his father's sister to wife--The Septuagint and Syriac versions render it "his cousin."
exo 6:23Elisheba--that is, Elizabethan. These minute particulars recorded of the family of Aaron, while he has passed over his own, indicate the real modesty of Moses. An ambitious man or an impostor would have acted in a different manner.