Thomas Aquinas Commentary Matthew 5:31-32

"It was said also, Whosoever shall put away his wife, let him give her a writing of divorcement: but I say unto you, that every one that putteth away his wife, saving for the cause of fornication, maketh her an adulteress: and whosoever shall marry her when she is put away committeth adultery." — Matthew 5:31-32 (ASV)

And it hath been said, Whosoever shall put away his wife, let him give her a bill of divorce. After having fulfilled the prohibitive precepts of the Law, the Lord now fulfills the permissive precepts of the Law. And this part is divided into two parts. Firstly, He fulfills the Law as to the permissive precepts, which pertain to God, and secondly, He fulfills those which pertain to one's neighbor, where it is said, You have heard that it hath been said: An eye for an eye.

The first part is divided into two sections. In the first section, He fulfills the permissive precept concerning the bill of divorce, and in the second section, another which is concerning an oath, where it is said, Again you have heard that it was said to them of old, thou shalt not forswear thyself.

In the first section He does two things: firstly, He relates the words of the Law, and secondly, He relates their fulfillment, where it is said, But I say to you, that whosoever shall put away his wife, etc.

He says, therefore, It hath been said, Whosoever shall put away his wife, etc. This precept is found in Deuteronomy 24:1.

Here there is a question. If someone shall put away his wife, let him give her a bill of divorce. This is the precept, but there is a permission to put away one's wife. Certainly Moses permitted this, but he did not command it.

Now permission is multiple, namely:

• Permission of concession, when lawful things are allowed, as for example, a monk is allowed by his abbot to visit his father.
• Permission of dispensation, when things which are not lawful become lawful through a dispensation, as for example, a monk is permitted by dispensation to eat meat with others.
• Permission of indulgence, when something lawful is permitted whose opposite is better, as for example, the Apostle's permission for second marriages (and yet continence of widowhood is better). According to this, you resolve what is said in the Gloss: namely, that the Apostles commanded second marriages, meaning that they permitted them; or it is a command if you do not wish to be continent; otherwise, it would not be binding as a precept.
• Permission of forbearance, as when God permits some evils to occur, although He always produces some good.
• Permission of tolerance, when some evil is tolerated, lest it become worse, as is the case here.

Whosoever shall put away his wife. Is not the inseparability of marriage from the law of nature? But is this, also, what was in the Mosaic law through dispensation: let him give her a bill of divorce, in which the reasons for the divorce were written?

Or [the reason for the bill] is otherwise, according to Josephus. Or it is thus according to Augustine: namely, that the reason why the bill was written was to cause a delay, so that the husband might be dissuaded by the counsel of the notaries from his purpose of divorce.

According to Jerome on this passage, the reason permission was given for divorcing a wife was the avoidance of wife-murder.

But was it lawful for the divorced wife to remarry? But I say to you, that whosoever shall put away his wife, excepting the cause of fornication, maketh her to commit adultery.

But there is a question: Is it lawful for a man to put away his wife for the cause of fornication? And it seems that it is not lawful, because evil ought not to be returned for evil.

I answer that the Lord allowed a man to put away his wife on account of fornication as a punishment for the one who was unfaithful. But is one bound by the precept to do this? I answer that the putting away of a wife guilty of fornication was prescribed in order that the wife’s crime might be corrected.

But can a man put her away on his own judgment? And he that shall marry her that is put away, committeth adultery, because the man that shall marry her is supervenient to marriage.