The traditional Reformed view of divorce is well expressed in Murray's Divorce and Adams' Marriage, Divorce and Remarriage, and nothing much more about that need be said. On this view, there are two grounds for divorce: one is sexual uncleanness, which includes adultery, but also the other sexual sins covered by the term porneia: homosexuality, bestiality, prostitution, etc. The other ground is desertion of a believing by an unbelieving spouse. Of course when a believing spouse is deserted by a professing believer, the professing believer (unrepentant) can be disciplined by the church, so that the situation becomes that of a believer divorced by an unbeliever. So in effect any desertion can be, with appropriate church involvement, ground for divorce.
Recently, however, some Reformed thinkers have thought that more needs to be said. Spouse abuse, for example, has become much more visible today (whether by an increase in its occurrence or an increase in its reporting is hard to say). Can spouse abuse be a ground for divorce?
I do believe that in a situation of spouse abuse, the abused partner, usually the wife, may be removed from the situation for her own safety. The sixth commandment would mandate that kind of self-defense. Of course, that creates an unbiblical marriage relationship; married couples ought to live together. But the responsibility for distorting the relationship rests with the abuser. And it is typical in Scripture for exceptions to be made to divine laws where human health and safety are at stake.
But can spouse abuse be a ground of divorce? Some have argued that it is a form of porneia, since porneia is used metaphorically for a wide variety of non-sexual sins. I do not think that path is promising. If we granted divorce for anything that could metaphorically be called porneia, we would have a liberal divorce policy indeed; but Matt. 19 makes clear that Jesus' own view of divorce was seen as so restrictive as to be virtually impossible to keep. Rather, I think we should limit the application of the porneia exception to those sins which are explicitly sexual in character.
But what of "desertion?" Could spouse abuse be a form of desertion? A prior question is this: Is it possible for a spouse to desert a marriage without physically leaving the home? The answer seems to be "yes." Certainly if a husband refuses to support his wife and children financially and continues unrepentant in that pattern, but continues to live with them under the same roof, we would conclude that he has "deserted" his family in the most significant sense. He has refused to take responsibility for them. He has broken his marriage vows and does not seek to renew his adherence to them.
It does seem to me that spouse abuse may also be a ground for divorce on the basis of "desertion." The unrepentant spouse abuser, too, has forsaken his marriage vow. He no longer loves, honors and cherishes his wife; rather he has become a threat to her life and health. This is not to say that a person once abused should file immediately for divorce. Opportunities for counseling and reconciliation should certainly be taken. (Even adultery in the most literal sense does not immediately necessitate divorce.)
I am also asked sometimes whether an adulterer (or one who is guilty of any marriage-breaking sin) who repents of his sin must be allowed by the innocent spouse to continue the marriage. I have held both views on this through my teaching career. Matt. 19 seems to teach that porneia itself, whether repented or not, can be ground for divorce, and I taught that early in my career. Later, however, I was moved to consider the concepts of repentance, forgiveness and reconciliation more deeply. If we argue that forgiveness means forgetting, such that the forgiven sinner bears no further consequences for his sin, then it would seem that it would be wrong to divorce a repentant adulterer. To do that would be to continue to hold forgiven sin against him, contrary to true forgiveness.
Still later in my reflections, however, I came to the conclusion that forgiving does not always mean forgetting, nor does it always mean that the person forgiven should bear no further consequences for his sin. Certainly when God forgives, he does not forget, nor does he absolve us of all earthly consequences for our sins, though he does absolve us of eternal punishment. Nor does the civil law "forget" the sins of those who repent of crimes. Even in personal relationships, forgiven sins cannot often be entirely forgotten. For one thing, to completely forget is often psychologically impossible. For another thing, it would be contrary to the truth simply to pretend that the sin never happened. Further, remembering past sins, even forgiven ones, may often be necessary in our dealings with people. If a teenager is guilty once of drunken driving, but repents, a parent may very well choose to allow him to keep driving-- both because he needs to drive and because he needs to sense the fulness of his restoration. But if a teenager habitually drinks and drives, contrary to his parents' commands and discipline, then the pattern cannot be "forgotten." The parent, in determining the punishment, cannot forget all the repented sins of the past. Rather he must punish the pattern. And that will generally result in a more severe punishment, for the good of the child and that of his potential victims.
It is scriptural for parents and churches to require repentant sinners to "bring forth fruits of repentance" before forgiveness culminates is "forgetting."
Therefore, I seem to be returning to my earlier view, which, again, is the apparent meaning of Matt. 19. Porneia, even when repented, may be so destructive of the "one flesh" bond between husband and wife that that bond cannot again be repaired. I believe I have seen cases in which that sort of rupture has taken place. When it has, the only remedy is divorce.
That of course makes it less easy to tell someone when he or she has, or does not have, grounds for divorce. Often answering that question requires heart searching. Priority should certainly be given to reconciliation, for God hates divorce (Mal. 2:16). But there are times when that is impossible, and it is hard for third parties to give advice in these cases. Difficult as it is to live with such ethical vagueness, it often appears in biblical teaching. This fact should not surprise us. Biblical ethics in general is an ethic of the heart.
Some of these thoughts have been gleaned from the report on Divorce and Remarriage, presented to the 20th PCA General Assembly (1982). It can be found in the PCA Digest Position Papers 1973-1993 (Atlanta: Committee for Christian Education and Publications, 1993), 182-293.