2 What then ought they to have done after this? Ought they not to have held their peace, and to have commended the saying? Ought they not to have marvelled at His wisdom? Ought they not to have stood amazed at His accordance with the Father? But none of these things do they, but as though they were contending for the law, they say, “How then did Moses command to give a writing of divorcement, and to put her away?” And yet they ought not now to have brought this forward, but rather He to them; but nevertheless He does not take advantage of them, nor does He say to them, “I am not now bound by this,” but He solves this too.
And indeed if He had been an alien from the old covenant, He would not have striven for Moses, neither would He have argued positively from the things done once for all at the beginning; He would not have studied to show that His own precepts agreed with those of old.
And indeed Moses had given many other commandments besides, both those about meats, and those about the Sabbath; wherefore then do they nowhere bring him forward, as here? From a wish to enlist the multitude of the husbands against him. For this was considered a thing indifferent with the Jews, and all used to do so much as this. Accordingly it was for this reason that when so many things had been said on the mount, they remembered this commandment only now.
Nevertheless, unspeakable wisdom makes a defense even for these things, and says, “Moses for the hardness of your hearts” thus made the law. And not even him does He suffer to remain under accusation, forasmuch as He had Himself given him the law; but delivers him from the charge, and turns the whole upon their head, as everywhere He does.
For again when they were blaming His disciples for plucking the ears of grain, He shows themselves to be guilty; and when they were laying a transgression to their charge as to their not washing their hands, He shows themselves to be the transgressors, and touching the Sabbath also: both everywhere, and here in like manner.
Then because the saying was hard to bear, and brought on them much blame, He quickly directs back His discourse to that ancient law, saying as He had said before also, “But in the beginning it was not so,” that is, God by His acts at the beginning ordained the contrary. For in order that they may not say, Whence is it manifest, that “for our hardness Moses said this?” hereby again He stops their mouths. For if this were the primary law, and for our good, that other would not have been given at the beginning; God in creating would not have so created, He would not have said such things.
“But I say unto you, Whosoever shall put away his wife except it be for fornication, and marry another, commits adultery.” For since he had stopped their mouths, He then gives the law with His own authority, like as touching the meats, like as touching the Sabbath.
For with regard to the meats likewise, when He had overcome them, then, and not till then, He declared unto the multitude, that, “Not that which goes in defiles the man;” and with regard to the Sabbath, when He had stopped their mouths, He says, “Wherefore it is lawful to do well on the Sabbath day;” and here this self-same thing.
But what took place there, this happened here also. For as there, when the Jews had been put to silence the disciples were troubled, and came unto Him with Peter and said, “Declare unto us this parable;” even so now also they were troubled and said, “If the case of the man be so, it is good not to marry.”
For now they understood the saying more than before. Therefore then indeed they held their peace, but now when there has been gainsaying, and answering, and question, and learning by reply, and the law appeared more clear, they ask Him. And openly to contradict they do not dare, but they bring forward what seemed to be a grievous and galling result of it, saying, “If the case of the man be so with his wife, it is not good to marry.” For indeed it seemed to be a very hard thing to have a wife full of every bad quality, and to endure a wild beast perpetually shut up with one in the house. And that you may learn that this greatly troubled them, Mark said, to show it, that they spoke to Him privately.
Source: Homilies on the Gospel of St. Matthew (New Advent)