Exodus 19:9

9.And the Lord said unto Moses. God here proclaims, that by a manifest symbol of His glory, He will make it evident that the Law proceeded not from Moses, but that he merely delivered faithfully what he received from heaven; for God was so covered with the cloud, as with a veil that He still upraised their minds as by a certain sign of His presence. On this was the authority of Moses founded, that the Israelites knew God to be the author of the doctrine, of which he was the minister. And this is especially worth remarking, because we gather from hence that there is no other mode of proving a doctrine, except by the assurance that it comes not from elsewhere, but from God alone; and thus is every mortal brought down to his level, lest any one, however excellent in wisdom, should dare to advance his own imaginations. For if the mightiest of prophets, Moses, obtained credit in the Church on no other grounds than because he bore the commands of God, and only taught what he had heard, how foolish and impudent will it be in teachers, who sink down far beneath him, to endeavor to attain a higher point! In fine, this passage shows that we must believe in God alone, but that at the same time we must listen to the prophets, who spoke out of His mouth. Besides this, it appears that God did not wish to obtain credit for His servant Moses during a short period of time, but that posterity should pay him the same reverence even after his death. The call of some is temporary; and it may happen that God takes away the spirit of prophecy from those to whom He has given it; but so did He appear to Moses, as to ratify, and, as it were, consecrate the truth of his doctrine in all ages. Thence it follows, that the brightness of God’s glory, which was shown to his ancient people in the thick cloud, is not yet extinct, but that it ought to illuminate the minds of all the godly, reverently to submit themselves to Moses. What follows at the end of the verse is a repetition from the last; for there was no intervening reply of the people which Moses could report. The meaning is, that although the Israelites had voluntarily promised to abide in the path of duty, yet that this confirmation was added, like a spur to those who are running, that they may proceed more nimbly.