Divorce, in canon law, signifies the dissolution of the marriage bond or the permanent separation of the parties, the bond remaining. A valid Christian marriage cannot be dissolved by any human power or for any cause except death.
Mal. 2:14-16 – You ask, “Why does he not?” Because the LORD was witness to the covenant between you and the wife of your youth, to whom you have been faithless, though she is your companion and your wife by covenant. 15 Has not the one God made and sustained for us the spirit of life? And what does he desire? Godly offspring. So take heed to yourselves, and let none be faithless to the wife of his youth. 16 “For I hate divorce, says the LORD the God of Israel, and covering one’s garment with violence, says the LORD of hosts. So take heed to yourselves and do not be faithless”.
Mt. 5:32-33 – But I say to you that every one who divorces his wife, except on the ground of unchastity, makes her an adulteress; and whoever marries a divorced woman commits adultery. 33 “Again you have heard that it was said to the men of old, ‘You shall not swear falsely, but shall perform to the Lord what you have sworn.’
Note: The RSVCE carries a note which reads: “unchastity”: The Greek word used here appears to refer to marriages which were not legally marriages, because they were either within the forbidden degrees of consanguinity (Lev. 18:6-16) or contracted with a gentile. The phrase except on the ground of unchastity does not occur in the parallel passage in Lk. 16:18. See also Mt. 19:19 (Mark 10:11-12), and especially Cor. 7:10-11, which shows that the prohibition is unconditional. The phrase, “except on the ground of unchastity”, should not be taken as indicating an exception to the principle of the absolute indissolubility of marriage which Jesus has just reestablished. It is almost certain that the phrase refers to unions accepted as marriage among some pagan peoples, but prohibited as incestuous in the Mosaic Law (cf. Lev. 18) and in rabbinical tradition. The reference, then, is to unions radically invalid because of some impediment. When persons in this position were converted to the true faith, it was not that their union could be dissolved; it was declared that they had never in fact been joined in true marriage, Therefore, this phrase does not go against the indissolubility of marriage, but rather reaffirms it.
On the basis of Jesus’ teaching and guided by the Holy Spirit, the Church has ruled that in the especially grave case of adultery it is permissible foe a married couple to separate, but without the marriage bond being dissolved; therefore, neither party may contract a new marriage.
Mt. 19:5-6 – For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh? 6 So they are no longer two but one flesh. What therefore God has joined together, let not man put asunder
Mt. 19:9 – And I say to you: whoever divorces his wife, except for unchastity, and marries another, commits adultery; and he who marries a divorced woman, commits adultery.
Mk. 10:11-12 – And he said to them, “Whoever divorces his wife and marries another, commits adultery against her; 12 and if she divorces her husband and marries another, she commits adultery”.
Lk. 16:1-18 – Every one who divorces his wife and marries another commits adultery, and he who marries a woman divorced from her husband commits adultery.
Rom. 7:2-3 – Thus a married woman is bound by law to her husband as long as he lives; but if her husband dies she is discharged from the law concerning the husband. 3 Accordingly, she will be called an adulteress if she lives with another man while her husband is alive. But if her husband dies she is free from that law, and if she marries another man she is not an adulteress.
1 Cor. 7:10-11 – To the married I give charge, not I but the Lord, that the wife should not separate from her husband 11 (but if she does, let her remain single or else be reconciled to her husband)–and that the husband should not divorce his wife.
Shepherd of Hermas [AD 140-155] “I said to [the shepherd]. ‘Sir, permit me to ask you a few questions.’ ‘Speak,’ he said. ‘Sir’ said I, ‘If someone has a wife faithful in the Lord, and he discovers her in some adultery, does the husband sin if he cohabits with her?’ ‘So long as he is ignorant,’ he said, ‘he does not sin; but if the husband knows her sin, and the wife does not repent, but continues in her fornication, and the husband cohabits with her, he makes himself a partner to her and an accomplish in her adultery.’ ‘What then, sir,’ said I, ‘shall the husband do, if the wife continue in this disposition?’ ‘Let him divorce her,’ he said, ‘and let the husband remain single. But if he divorces his wife and marry another, he too commits adultery'” (Mand. 4, 1, 4).
St. Justin Martyr [AD 148-155] “In regard to chastity, he has this to say: ‘If anyone look with lust at a woman, he has already before God committed adultery in his heart.’…And, ‘Whoever marries a woman who has been divorced from another husband, commits adultery.’…According to our Teacher, just as they are sinners who contract a second marriage, even though it be in accord with human law, so also are they sinners who look with lustful desire at a woman” (First Apology 15).
Origen [post AD 244] “A wife is bound for so long a time as her husband lives; but if her husband is put to rest, she is free to marry whom she will, only be it in the Lord” (Commentaries on Matthew 4, 23).