Commentaries:
Here, Paul is relaying God's opposition to separation and divorce because they are obviously a result of a lack of peace. It is for this very reason that God hates divorce so much. Divorce creates not peace and unity but war and division. Among us, it should be a last resort.
Why? He tells us simply that we have been called to peace (verse 15). When we divorce, we are not making peace. We are actually going to war and causing separation. But God allows it, He says, in situations in which the relationship has been so undermined by sin (like adultery) that peace is impossible. Trust has been ruined. It takes quite a person to return to a loving relationship after such divisive, perfidious things have happened. It can be done, but He allows divorce because God considers peace more important.
So, the child of God must strive to do his or her part to make and maintain peace, especially in a marriage, even if the other spouse is an unbeliever. We should endeavor to make it work because that our election binds us to do just that. We have been called to be peacemakers, not to be disruptors, not to revel in conflict, but to make peace.
Richard T. Ritenbaugh
The Peacemakers