Jesus defined adultery to include those who divorce and remarry for any reason other than fornication. Fornication is extra-marital sex. Christ also included those who marry the divorced person as also committing adultery. Jesus declared in Mark 10:11–12, “If one divorced his woman and married another, he is committing adultery against her. And if a woman divorced her man and married another, she is committing adultery.” Note that the divorce and the remarriage are in the past tense while adultery is in the present active tense in Mark 10 as is also in Matthew 19. This shows the active state of adultery when one has married another for another reason other than fornication. Notice that marrying another is adultery against the previous spouse, and that adultery is a transgression against a spouse.
Jesus declared in Luke 16:18, “Everyone divorcing his woman and marrying another is committing adultery; and everyone marrying her who has been divorced from a man is committing adultery.” In Luke 16:18, Jesus teaches that adultery includes when a person divorces and marries another. The adultery begins with the new marriage and continues in an adulterous marriage.
One can only divorce and remarry for one exception. Jesus mentioned that one exception when Jesus declared in Matthew 19:9, “And I say to you that if one divorced his woman, not upon extramarital sex, and married another, he is committing adultery, and he who married the divorced is committing adultery.” If a person finds that one’s spouse was fornicating with another person before or during the marriage, that person is able to divorce and marry another by giving a note for the reason of the divorce being fornication (Matt 5:31–32).
In Matthew 5:32, Jesus said that the spouse divorcing another for any other reason than fornication is guilty of causing adultery when the other spouse marries another. The one divorcing must divorce by “a word of fornication” that is a note given to the adulterous spouse. Jesus proclaimed in Matthew 5:31–32,
And it was said that if one divorced his woman, he must give her a notice of divorce. And I say to you that if one divorced his woman without a word of fornication, he makes her to commit adultery, and if one married the divorced, he is committing adultery.
These previous quotes of Jesus contain precise grammar with the original tenses of each verb and participle. The Greek word apoluo, which is often translated “divorced” or “put away,” occurs 69 times in the New Testament, and yet the word is only used 14 times to refer to divorce and 55 times to mean “put away,” “release,” and even “forgive” by releasing sins (Luke 6:37ff). The Greek apoluo includes two parts. These are the prefix apo meaning “from” and the verb luo meaning “loose.” Apoluo expresses the idea to release or lose someone or something.
Jesus apparently defined adultery to include divorce and remarriage, and He taught that adultery is against the divorced spouse (Mark 10:11–12). One’s eligibility to remarry is dependent upon whether a person is committing adultery by remarrying. This requires repentance as Christ calls sinners to do (Luke 5:32; 13:3, 5). Repentance is essential for the forgiveness of sins (Luke 24:46–47). God will forgive the guilty and once adulterous person after that person has repented, confessed that sin to God, and confessed repentance to the previous spouse (Matt 5:23–24; 18:15–17, 21-22; Luke 17:3–4). Forgiveness requires repentance from adultery. If a person’s remarriage is not adulterous when the previous spouse has married another, then that person’s remarriage is not adulterous when the previous spouse has died (Mark 10:11; Rom 7:3; 1 Cor 7:39).
In conclusion, Jesus is very clear that those who have divorced and remarried another except for fornication or have married the divorced, are presently committing adultery against the previous unmarried spouse. Adultery defiles the marriage bed (Heb 13:4). Jesus’ instructions about divorce, remarriage, and adultery are just as much in effect as all of His instructions are in effect before and after people are aware of them (Matt 19:11). As Jesus proclaimed, “What therefore God has joined together, let no one separate” (Mark 10:9).