1 Corinthians 7:15
But if the unbelieving depart, let him depart. A brother or a sister is not under bondage in such [cases]: but God hath called us to peace.
Note 18 at 1Co 7:15: Many sincere people differ on their interpretation of what this verse means when it says that believers are "not under bondage in such cases." The liberal interpretation would be that Paul was saying they are free to remarry if their unsaved mates divorce them. The conservative view would be that Paul was saying they do not have any obligation to fight to hold the marriage together. Let the unbelievers divorce, but remarriage is still not an option, as stated in 1Co 7:11.