If a Christian gets a divorce and remarries, is he or she guilty of a continuous sin for as long as the new marriage continues?
Any marriage that takes place following a divorce while the ex-spouse is still alive is an act of adultery, according to Jesus (you can read why in our article on Divorce), but is the marriage invalid? Does the couple continue to commit adultery for as long as they remain married? Does God require the couple divorce to correct for the earlier sin of adultery?
In a word, no. Jesus says this in Matthew 19:
It's important to recognize that Jesus didn't say that the new marriage after divorce was adultery (i.e., the marriage itself is adulterous). Rather, Jesus said that the one who enters into a marriage after divorce commits adultery (i.e., the person is guilty of sin for having married again). In other words, the institution itself isn't sinful or illegitimate, but rather the person's choice to enter into the institution was sin yet the institution itself is still valid.
In fact, Jesus said the man "marries" another woman, Jesus' choice of words make clear a new union has been formed, and once a marriage is formed through an exchange of vows and a "one-flesh" relationship, a valid covenant is established and must be honored like all marriages. The man and woman are expected to remain faithful to each other until death.
We see this principle at work in many places in the Bible including in the account of Jacob. Jacob was deceived into marrying Leah instead of Rachel. Did this mean his marriage with Leah was invalid? No. Furthermore, Jacob wrongly continued to pursue marriage with Rachel despite already being married to Leah. Jacob's eventual marriage to Rachel was formed through an act of adultery against Leah, yet the Bible never discredits Jacob's later marriages. They are viewed in Scripture as entirely valid unions. Therefore, every marriage covenant must be honored, even one that is formed through an act of adultery.
Moreover, adultery does not describe the act of sex, per se, but rather the breaking of a marriage vow through an act of sex. Once a marriage vow has been broken by an act of adultery, it cannot be said to be "re-broken" each time the couple has sex. It was simply broken once regardless of how many times sex took place. So while the consequences of adultery may last forever, the act itself is over in a moment.
For example, murder is a sin that occurs in a moment, yet results in consequences that continue afterward (i.e., the murder victim remains dead thereafter). Nevertheless, we wouldn't say that the sin of murder is "continuous" simply because the victim remains dead. We understand that the sinful act occurred in a moment yet it resulted in ongoing consequences. Likewise, we don't say that adultery is "continuous" because someone remains married to a new spouse following divorce. We understand that the marriage was formed through an act of adultery in a moment resulting in a new marriage that is valid and must be honored thereafter.
So when a person remarries following a divorce, that person commits adultery against the first spouse. At the same time, they enter into a legitimate marriage that is binding for life. The person may not divorce the second spouse even to seek reconciliation with the first spouse since this would be a new act of sin, and the Lord doesn't command us to commit new sins in an effort to correct for past sins.
In fact, God's word does not even allow a first marriage to be reconciled once a second marriage had been formed. Moses taught Israel that if a couple divorces and then one remarries, the first marriage may never be reconciled:
A woman who divorces and remarries and then divorces a second time was not permitted to return to her first husband even if he would have her. The woman's second marriage precluded reconciliation with her first husband because she was required to honor her second marriage until death, and reconciliation with her first husband would require an act of adultery against her second husband. This is further proof to us that God views a second marriage as legitimate and binding.
In short, every marriage is considered legitimate, and the Lord expects us to honor whatever marriage we have. Even though a second marriage is considered an act of adultery, the sin of adultery is not ongoing because the new marriage is valid. Therefore, the new marriage is legitimate and must be honored.
If a Christian has divorced and remarried, he or she should acknowledge and repent of the sin of adultery, and then both spouses should honor the new marriage in peace knowing that they are forgiven their sins in Christ. From that point forward, they must commit to remaining faithful to this new marriage until death.