Matthew 19:8

Nevertheless, unspeakable wisdom maketh a defense even for these things, and saith, "Moses for the hardness of your hearts" thus made the law. And not even him doth 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 doth. For again when they were blaming His disciples for plucking the ears of corn, 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 stoppeth 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.

What He says is to this purpose. Is it possible that God should so contradict Himself, as to command one thing at first, and after defeat His own ordinance by a new statute? Think not so; but, whereas Moses saw that through desire of second wives who should be richer, younger, or fairer, that the first were put to death, or treated ill, he chose rather to suffer separation, than the continuance of hatred and assassination. Observe moreover that He said not God suffered you, but, Moses; showing that it was, as the Apostle speaks, a counsel of man, not a command of God. (1 Cor. 7:12.)

Therefore said He well, Moses suffered, not commanded. For what we command, that we ever wish; but when we suffer, we yield against our will, because we have not the power to put full restraint upon the evil wills of men. He therefore suffered you to do evil that you might not do worse; thus in suffering this he was not enforcing the righteousness of God, but taking away its sinfulness from a sin; that while you did it according to His law, your sin should not appear sin.

(ubi sup.) For how great was that hardness! When not even the intervention of a bill of divorce, which gave room for just and prudent men to endeavour to dissuade, could move them to renew the conjugal affection. And with what wit do the Manichæans blame Moses, as severing wedlock by a bill of divorce, and commend Christ as, on the contrary, confirming its force? Whereas according to their impious science they should have praised Moses for putting asunder what the devil had joined, and found fault with Christ who riveted the bonds of the devil.