“I tell you that anyone who divorces his wife, except for marital unfaithfulness, and marries another woman commits adultery.”
It appears that Jesus gives Biblical grounds for divorce in the event of marital unfaithfulness by a spouse. Jesus was clarifying the law of Moses which allowed for divorce. This was allowed as a concession because the people’s hearts were hard but Jesus makes it clear that they should not remarry.
What is marital unfaithfulness? The Greek word is porneia. It is where we get the English word pornography. It appears 24 times in the New Testament. In the King James version it is translated as fornication every time. Other English translations in some way or other imply that it is sexual immorality that is taking place. So marital unfaithfulness should best be understood as a sexual act outside of marriage.
Jesus never gives an explanation on why divorce is allowed in the event of marital unfaithfulness. The simplest solution is that a person who has been unfaithful has already broken their marriage vow and therefore if their spouse divorces them they are not the one guilty of breaking the marriage vow.
Another explanation, although not without problems, concerns the penalty for those caught in adultery. Leviticus 20:10 states “If a man commits adultery with another man’s wife—with the wife of his neighbor—both the adulterer and the adulteress must be put to death.” If an adulterer is put to death then there is no problem divorcing or remarrying because a person is free to remarry after their spouse has died.
The first problem with this is a logical one. If an adulterer is put to death, there would be no need to go through with a divorce unless it was symbolic.
The bigger problem is that this law was not practiced evenly if it all. King David was not only an adulterer but a murderer and did not face death. God actually instructed Hosea to marry a prostitute of all people. And Jesus prevents the Pharisees from upholding the law in John 8 when they catch a woman in adultery. Instead of judging her for her sin, He simply instructs her to go and sin no more.
Marital unfaithfulness may be grounds for divorce and it is certainly a sign of much deeper problems within a marriage. This does not mean that the marriage can’t be salvaged however. It is cause for a divorce but God still desires peace and harmony. He also desires a repentant heart. A person who has been unfaithful in their marriage deserves another chance if they are truly repentant. King David committed awful sins but he was still considered a man after God’s own heart.
The truly difficult part of divorce and marital unfaithfulness is that we can never be certain of a person’s heart. Only God knows a person’s heart for certain. For a marriage to withstand a partner being unfaithful, it takes a tremendous amount of faith in a person’s ability to change and also in God to help that person and the marriage.