Paul does not deny that there was splendor in the law and on the face of Moses, but it did not endure because in his case it was a symbol and not a reality. The difference between the face of Moses and the glory of Christ is the same as the difference between the picture and the person whom it portrays.
Next, he sets on foot yet another argument to prove the superiority also from a fresh ground. What then is this argument? That based upon duration, saying, "For if that which passeth away was with glory, much more that which remaineth is in glory." For the one ceased, but the other abideth continually.
He presents another syllogism. If the law that was ceasing and subject to abolition was given in glory, then how much more shall the law that is unshakeable and eternal – the New Testament – be in glory.
Then he assigns the cause of this when he says, For if what faded away came with glory, what is permanent must have much more glory. His reasoning is thus: that which was given to pass away is nothing in relation to that which is given to remain always. If, therefore, the Old Testament, which is rendered void, is done away with: "But when the perfect comes, the imperfect will pass away" (1 Cor. 13:10). For with glory the ministry of Moses came, at least with a particular glory. And it is obvious that the New Testament remains, because it is begun here and completed in heaven: "Heaven and earth shall pass away, but my words shall not pass away" (Lk. 21:33). It will be much more in eternal glory, in which it will be perfected; it will be, I say, for us who are its ministers.
[AD 384] Ambrosiaster on 2 Corinthians 3:11