Why then did Moses order? They had thought of this calumny, [1] if, which was more probable, Christ should demand a proper cause to be shown in cases of divorce; for it appears that whatever God permits by his law, whose will alone establishes the distinction between what is good or evil, is lawful. But Christ disarms the falsehood and slander by the appropriate reply, that Moses permitted it on account of their obstinacy, and not because he approved of it as lawful. And he confirms his opinion by the best argument, because it was not so at the beginning. He takes for granted that, when God at first instituted marriage, he established a perpetual law, which ought to remain in force till the end of the world. And if the institution of marriage is to be reckoned an inviolable law, it follows that whatever swerves from it does not arise from its pure nature, but from the depravity of men. But it is asked, Ought Moses to have permitted what was in itself bad and sinful? I reply, That, in an unusual sense of the word, he is said to have permitted what he did not severely forbid; [2] for he did not lay down a law about divorces, so as to give them the seal of his approbation, but as the wickedness of men could not be restrained in any other way, he applied what was the most admissible remedy, that the husband should, at least, attest the chastity of his wife. For the law was made solely for the protection of the women, that they might not suffer any disgrace after they had been unjustly rejected. Hence we infer, that it was rather a punishment inflicted on the husbands, than an indulgence or permission fitted to inflame their lust. Besides, political and outward order is widely different from spiritual government. What is lawful and proper the Lord has comprehended under the ten words. [3] Now as it is possible that many things, for which every man's conscience reproves and charges him, may not be called in question at a human tribunal, it is not wonderful if those things are connived at by political laws. Let us take a familiar instance. The laws grant to us a greater liberty of litigation than the law of charity allows. Why is this? Because the right cannot be conferred on individuals, unless there be an open door for demanding it; and yet the inward law of God declares that we ought to follow what charity shall dictate. And yet there is no reason why magistrates should make this an excuse for their indolence, if they voluntarily abstain from correcting vices, or neglect what the nature of their office demands. But let men in a private station beware of doubling the criminality of the magistrates, by screening their own vices under the protection of the laws. For here the Lord indirectly reproves the Jews for not, reckoning it enough that their stubbornness was allowed to pass unpunished, if they did not implicate God as defending their iniquity. And if the rule of a holy and pious life is not always, or in all places, to be sought from political laws, much less ought we to seek it from custom.

Footnotes

1 - "Ils avoyent songe ceste calomnie pour l'avoir toute preste;" -- "they had thought of this calumny, to have it all ready."

2 - "Ie repond, Qu'a parler proprement, il ne l'a pas permis: mais d'autant qu'il ne l'a pas defendu estroittement, il est dit qu'il l'a permis;" -- "I reply, That, strictly speaking, he did not permit it; but in so far as he did not strictly forbid it, he is said to have permitted it."

3 - Where the English version gives the words, ten commandments, the phrase in the original Hebrew is, srt hdvrym, the ten words, (Exodus 34:28; Deuteronomy 4:13; 10:4.) -- Ed

Why did Moses - To this they objected that Moses had allowed such divorces Deuteronomy 24:1; and if he had allowed them, they inferred that they could not be unlawful. See the notes at Matthew 5:31.

Why did Moses then command to give a writing of divorcement? - It is not an unusual case for the impure and unholy to seek for a justification of their conduct from the law of God itself, and to wrest Scripture to their own destruction. I knew a gentleman, so called, who professed deep reverence for the sacred writings, and, strange as it may appear, was outwardly irreproachable in every respect but one; that was, he kept more women than his wife. This man frequently read the Bible, and was particularly conversant with those places that spoke of or seemed to legalize the polygamy of the patriarchs!
A writing of divorcement - See the form of it in the note on Matthew 5:31 (note).

(2) They say unto him, Why did Moses then command to give a writing of divorcement, and to put her away?
(2) Because political laws are adjusted to allow some things, it does not follow that God therefore approves of them.

They say unto him,.... That is the Pharisees, who object the law of Moses to him, hoping hereby to ensnare him, and expose him to the resentment of the people, should he reject that, as they supposed he would;
why did Moses then command to give a writing of divorcement, and put her away? referring to Deuteronomy 24:1 which they thought to be a contradiction, and what they knew not how to reconcile to the doctrine Christ had delivered, concerning the original institution of marriage, and the close union there is between a man and his wife, by virtue of it, and which is not to be dissolved by men. Concerning a writing of divorcement and the form, and manner of it; see Gill on Matthew 5:31

They say unto him, Why did Moses then command to give a writing of divorcement, and to put her away?

Why then did Moses command? Deuteronomy 24:1-4. They insinuate that he contradicts Moses.
Moses, for your hardness of heart. Moses "suffered" some things that were not right on account of "the hardness of your heart," a low state of morals. A people cannot be lifted from moral depravity to a high standard at once. Hence the law permitted some things that were below the perfect standard of Christ.
In the beginning. In the beginning there was no divorce and no polygamy. The first polygamist was the race of Cain (Genesis 4:19).

Why did Moses command - Christ replies, Moses permitted (not commanded) it, because of the hardness of your hearts - Because neither your fathers nor you could bear the more excellent way. Deuteronomy 24:1; Matthew 5:31; Mark 10:2; Luke 16:18.