Question: "Is remarriage after divorce always adultery?"
Answer: Before we even begin to answer this question, let us reiterate, "God hates divorce" (Malachi 2:16). The pain, confusion, and frustration most people experience after a divorce are surely part of the reason that God hates divorce. Even more difficult, biblically, than the question of divorce, is the question of remarriage. The vast majority of people who divorce either remarry or consider getting remarried. What does the Bible say about this?
Matthew 19:9 says, "I tell you that anyone who divorces his wife, except for marital unfaithfulness, and marries another woman commits adultery." See also Matthew 5:32. These Scriptures clearly state that remarriage after a divorce is adultery, except in the instance of "marital unfaithfulness." In regards to this "exception clause" and its implications, please read the following articles:
What does the Bible say about divorce and remarriage?
I am divorced. Can I remarry?
It is our view that there are certain instances in which divorce and remarriage are permitted without the remarriage being considered adultery. These instances would include unrepentant adultery, physical abuse of spouse or children, and abandonment of a believing spouse by an unbelieving spouse. We are not saying that a person under such circumstances should remarry. The Bible definitely encourages remaining single or reconciliation over remarriage (1 Corinthians 7:11). At the same time, it is our view that God offers His mercy and grace to the innocent party in a divorce and allows that person to remarry without it being considered adultery.
A person who gets a divorce for a reason other than the reasons listed above, and then gets remarried has committed adultery (Luke 16:18). The question then becomes, is this remarriage an "act" of adultery, or a "state" of adultery. The present tense of the Greek in Matthew 5:32; 19:9; and Luke 16:18 can indicate a continuous state of adultery. At the same time, the present tense in Greek does not always indicate continuous action. Sometimes it simply means that something occurred (Aoristic, Punctiliar, or Gnomic present). For example, the word "divorces" in Matthew 5:32 is present tense, but divorcing is not a continual action. It is our view that remarriage, no matter the circumstances, is not a continual state of adultery. Only the act of getting remarried itself is adultery.
In the Old Testament Law, the punishment for adultery was death (Leviticus 20:10). At the same time, Deuteronomy 24:1-4 mentions remarriage after a divorce, does not call it adultery, and does not demand the death penalty for the remarried spouse. The Bible explicitly says that God hates divorce (Malachi 2:16), but nowhere explicitly states that God hates remarriage. The Bible nowhere commands a remarried couple to divorce. Deuteronomy 24:1-4 does not describe the remarriage as invalid. Ending a remarriage through divorce would be just as sinful as ending a first marriage through divorce. Both would include the breaking of vows before God, between the couple, and in front of witnesses.
No matter the circumstances, once a couple is remarried, they should strive to live out their married lives in fidelity, in a God-honoring way, with Christ at the center of their marriage. A marriage is a marriage. God does not view the new marriage as invalid or adulterous. A remarried couple should devote themselves to God, and to each other – and honor Him by making their new marriage a lasting and Christ-centered one (Ephesians 5:22-33).