Now before we go on to Jesus’ teachings, we need to consider other portions of 1 Corinthians 7:
12 To the rest I say this (I, not the Lord): If any brother has a wife who is not a believer and she is willing to live with him, he must not divorce her. 13 And if a woman has a husband who is not a believer and he is willing to live with her, she must not divorce him. 14 For the unbelieving husband has been sanctified through his wife, and the unbelieving wife has been sanctified through her believing husband. Otherwise your children would be unclean, but as it is, they are holy. 15 But if the unbeliever leaves, let him do so. A believing man or woman is not bound in such circumstances; God has called us to live in peace. 16 How do you know, wife, whether you will save your husband? Or, how do you know, husband, whether you will save your wife?
This passage is sometimes referred to as the Pauline Exception. It is argued that this creates a second exception to the prohibition on divorce — the first exception being fornication, as declared by Jesus and the second being an unbelieving spouse.
Interestingly, Paul never mentions fornication nor does he speak of remarried spouses being guilty of adultery. While Paul is obviously aware of Jesus’ teaching on divorce (7:10), he doesn’t remotely speak in those terms. Paul’s teaching is simple. It’s wrong to violate the marriage covenant. And it’s always better to be single to better serve the Lord. But neither marriage nor remarriage is a sin.
Paul is not creating an exception to the command to not divorce. He is simply giving the practical advice that if an unbelieving spouse divorces the believing spouse, the believer is not a sinner and is not bound to pretend to be married to someone with whom he or she is no longer united. On the other hand, Paul plainly says that a believer must honor the marriage covenant so long as the unbeliever permits that marriage to last.
Paul is not authorizing a divorce. He is simply pointing out that a Christian is only bound to his or her unbelieving spouse so long as the unbelieving spouse is willing to remain married. The phrase “God has called us to peace” is of rabbinic origin. It’s what the rabbis said when reaching a pragmatic conclusion not necessarily dictated by the Law of Moses.
Paul’s words in 1 Corinthians 7:15 is better translated “you are no longer enslaved” (the Greek is quite clear). It’s a bit shocking for us to hear Paul referring to marriage as slavery, and so many modern translations (such as the NIV) soften the words. However, the Jewish certificate of divorce and certificate of freedom for a slave were virtually identical documents, and much of rabbinic divorce law came from Exodus 21:10-11, which is speaks of marrying a slave girl. Therefore, the metaphor is a clear allusion to a standard Jewish certificate of divorce, which always allowed remarriage. In fact, the very purpose of the certificate was to allow remarriage.
May the Christian spouse remarry in such a case? Of course. As explained above, verses 27-28 say so.
 Instone-Brewer, p. 203. For example, an imbecile could not be prosecuted for theft but nonetheless the stolen goods were confiscated and return to their right owner “for the sake of peace” in rabbinic teaching.
 In Divorce, Repentance, and the Gospel of Christ (Gospel Enterprises, 1981) (hereafter, “Hicks”), Olan Hicks quotes Alexander Campbell, one of the founders of the Restoration Movement, who responded to a question about a woman who had been abandoned by her husband and then sought a formal divorce, as follows:
If in that matter she had actually erred, she is not now to be repudiated for that error any more than one who formerly was a slanderer or a persecutor, and has been brought to repentance and reformation, is now to be rejected for crimes committed before his conversion. And if the divorce was obtained after she became a disciple, in order to conform to the statutes of the state, with express reference to her marriage, it seems not to materially alter the case.
Campbell noted that Walter Scott concurred in his judgment. Scott, another Restoration leader, invented such notable slogans as the “five finger exercise” of “hear, believe, repent, confess, and be baptized” and introduced the use of the gospel invitation after each sermon.