Jesus talks about remarriage and adultery in Matthew 5:31-32. He says that anyone who divorces his faithful wife causes her to commit adultery (presumably when she remarries). Similarly, anyone who marries a divorced woman commits adultery. In Mark 10:11-12, He explains that anyone who divorces a faithful spouse and remarries also commits adultery. With all these stipulations, when is it not adulterous to remarry after a divorce?
If a person divorces and remarries, is it always going to be adulterous?
There are three specific instances in which it is not adultery to remarry. The first is if the divorce occurred because of adultery and the faithful spouse remarries. The second is if a person remarries after the death of a spouse who had divorced that person unbiblically. Death releases the innocent party (1 Corinthians 7:39). The final case is if a divorced couple, who did not remarry other people, reconcile their own relationship (1 Corinthians 7:11). These are the only situations specifically mentioned in the Bible.
Does this mean God will never allow anyone else to remarry? Where the Bible does not say directly, we must infer from other passages. We know that God forgives all sins (1 John 1:9), removing them from our lives (Psalm 103:12). It's possible that God may allow remarriage, possibly if the divorce occurred because of abuse (one potential meaning of hard-heartedness found in Matthew 19:8) or abandonment (1 Corinthians 7:15). Any of those situations would take serious prayer and leading by the Holy Spirit.
It needs to be clear that if a divorced person does remarry unbiblically, the sin is in the decision and act of remarrying; being in a marriage that was formed against the teaching of Scripture is not a state of sin. Despite the origin of the marriage, God still joined the two together. The couple should not divorce, which would be adding sin to sin, and should not let anyone compel them to consider divorce (Matthew 19:6). The adultery occurred between the decision to marry and the wedding day; it does not continue every time the couple consummates their marriage or in their day-to-day married lives. No matter how friends and family feel about the new spouse or the conditions surrounding the wedding, they are still obliged to support and encourage the new marriage.
What grounds for divorce does the Bible provide?
Can widows / widowers remarry? What is the biblical view of remarriage after death of a spouse?
What is the biblical view on divorce and remarriage?
Can a divorced person remarry?
Biblically, what constitutes a marriage?
Truth about Marriage