Divorce and Remarriage
According to the teaching of the Church, if a couple is validly married, nothing but death can break the marriage bond. Therefore, divorce is not allowed: "Every one who divorces his wife and marries another commits adultery, and he who marries a woman divorced from her husband commits adultery" (Luke 16:18; Mark 10:11-12); "A married woman is bound by law to her husband as long as he lives . . . Accordingly, she will be called an adulteress if she lives with another man while her husband is alive" (Rom. 7:2-3); "To the married I give charge, not I but the Lord, that the wife should not separate from her husband (but if she does, let her remain single or else be reconciled to her husband)–and that the husband should not divorce his wife" (1 Cor. 7:10). Jesus restored marriage to the status of a sacrament, just as it was between Adam and Eve, and therefore, marriage now binds for life.
Those who argue in favor of divorce and remarriage cite Matthew: "Whoever divorces his wife, for any reason other than her unfaithfulness, and marries another, commits adultery" (Matt. 19:9). This, they say, means that divorce is possible if one of the spouses is "unfaithful". Whatever the meaning of the word "unfaithful", it is clear that Jesus is not permitting remarriage in this case, because He did not say "and marries another for any reason other than her unfaithfulness", He said it after "whoever divorces his wife". What Jesus was permitting here was separation, not divorce. After all, when Jesus was asked, "Is it lawful for a man to divorce his wife for any cause whatever", He responded by saying, "They [the married couple] are no longer two, but one flesh. Therefore, what God has joined together, no human being must separate" (Matt. 19:3-6). There is no cause, Jesus makes clear, that one may divorce and remarry (see parallel passages in Mark and Luke).
Hermas (The Shepherd 4:1:6 [A.D. 80]) "What then shall the husband do, if the wife continue [to commit adultery]? Let him divorce her, and let the husband remain single. But if he divorce his wife and marry another, he too commits adultery".
Clement of Alexandria (Miscellanies 2:23:145:3 [A.D. 208]) "That Scripture counsels marriage, however, and never allows any release from the union, is expressly contained in the law".
Origen (Commentaries on Matthew 14:24 [A.D. 248]) "Just as a woman is an adulteress, even though she seem to be married to a man, while a former husband yet lives, so also the man who seems to marry her who has been divorced does not marry her, but, according to the declaration of our Savior, he commits adultery with her" .
Council of Elvira (Canon 9 [A.D. 300]) "A woman of the faith who has left an adulterous husband of the faith and marries another, her marrying in this manner is prohibited. If she has so married, she may not receive Communion–unless he that she has left has since departed from this world".
Ambrose of Milan (Abraham 1:7:59 [A.D. 387]) "No one is permitted to know a woman other than his wife. The marital right is given you for this reason: lest you fall into the snare and sin with a strange woman. ‘If you are bound to a wife do not seek a divorce'; for you are not permitted, while your wife lives, to marry another" .
Jerome (Letters 55:3 [A.D. 396]) "So long as a husband lives, be he adulterer, be he sodomite, be he addicted to every kind of vice, if she left him on account of his crimes, he is her husband still and she may not take another"; (Commentaries on Matthew 3:19:9 [A.D. 398]); "Wherever there is fornication and a suspicion of fornication, a wife is freely dismissed. Because it is always possible that someone may calumniate the innocent and, for the sake of a second joining in marriage, act in criminal fashion against the first, it is commanded that when the first wife is dismissed, a second may not be taken while the first lives".
Augustine (Adulterous Marriages 1:9:9 [A.D. 419]) "Neither can it rightly be held that a husband who dismisses his wife because of fornication and marries another does not commit adultery. For there is also adultery on the part of those who, after the repudiation of their former wives because of fornication, marry others"; (ibid., 2:4:4) "A woman begins to be the wife of no later husband unless she has ceased to be the wife of a former one. She will cease to be the wife of a former one, however, if that husband should die, not if he commit fornication".