It is not a coincidence that Christ teaches on divorce in the passage immediately following His instruction on lust. And although Christ taught in this section that we should be willing to remove any member which stumbles us, He teaches here that there is one member which is not to be removed. “”Furthermore it has been said, ‘Whoever divorces his wife, let him give her a certificate of divorce.’ But I say to you that whoever divorces his wife for any reason except sexual immorality causes her to commit adultery; and whoever marries a woman who is divorced commits adultery” (Matt. 5:31-32).
What did Moses teach about divorce? When we compare this passage with Matthew 19, we see that we must first consider Moses. The teaching of Moses on divorce is given in Deuteronomy 24:1-4. There are three basic truths which must be understood from that passage.
1. Divorce was limited by this law to certain specified causes. A man could not divorce his wife for trifling reasons; it had to be for “uncleanness.” And, of course, given the larger pattern of Mosaic law, this uncleanness could not just be asserted, it had to be established by at least two witnesses.
2. If he divorced his wife, a man also had to give his wife a bill of divorce. The process of divorce was thus made a formal judicial act. It would force men to think about the solemnity of what they were doing.
3. A man who put away his wife could not have her back if she had married another man in the intervening time. In a very real sense, he was quite possibly burning his bridges. As a side note, there is a real possibility here that Moses was prohibiting a man from profiting financially from this kind of thing. If he divorced his wife “for cause,” he owed her nothing financially, and if she married again she gained financially from her second husband. This meant the first husband could not “forgive” her because it was now financially lucrative for him to do so.
Now the context of this exchange is that Christ was teaching against the Pharisees, and not against Moses. This is clear from the encounter in Matthew 19. The Pharisees were saying that Moses commanded divorce, when he had done nothing of the kind (v. 7). And so what was the Pharisaic question there? Could a man put his wife away for “just any reason?” In other words, the “heirs” of Moses were using the words of Moses to recreate the very situation — easy divorce — which the law of Moses sought to restrain.
We now can consider the teaching of Christ. First, Christ teaches us that marriage is not absolute. The bond that unites a man and woman is not metaphysical; it is covenantal. This is very important. Under the law of God, marriage can be lawfully dissolved.
But secondly, the reasons for such dissolution are not to be found in the whims of men. “She burned the toast.” “I found someone prettier.” A man cannot avoid adultery (in the sight of God) just because he has a good lawyer and gets the right paperwork done. The ground that Christ mentions here as a legitimate basis for divorce is that of general sexual uncleanness.
How does this line up with what St. Paul taught about divorce? Jesus was teaching Israel — the covenant people of God. They had the law of God, and marriages were ordinarily between covenant members. In such a covenantal context, Christ taught that the only grounds for dissolution of marriage was porneias.
But when the gospel went out to the nations, the result of this great expansion was a huge increase in the number of mixed marriages. This context gives us the interesting expression and teaching of the apostle Paul — not I, but the Lord and I, not the Lord (1 Cor. 7:10-16; 27-28). But St. Paul and Christ are not at variance; they are addressing different situations. Between two professing Christians, divorce is only permitted on grounds of infidelity. In a mixed marriage, if the unbeliever wants to go, then the believer is not bound.
For one other variation, we must also remember Ezra 9-10. Sometimes divorce is a proper response when the more serious action required by the law of God is not permitted — say, by the civil magistrate.