1 Corinthians 7:10-14
1Co 7:10 But for those of you already married, I have a command (not from me, but from the Lord): a wife should not leave her husband.
1Co 7:11 But if she does leave, she should stay unmarried, or else be reconciled to her husband. And a husband should not divorce his wife.
1Co 7:12 To the rest of you, I advise this (I, not the Lord): if a brother has an unbelieving wife, and she consents to live with him, he should not divorce her.
1Co 7:13 And if any wife has a husband who is an unbeliever, and he consents to live with her, she should not divorce her husband.
1Co 7:14 Since the unbelieving husband is being made holy by his wife, and the unbelieving wife is being made holy by her husband. Otherwise your children would be unclean, but now, they are being made holy.
stay if you can
There appears to be a lot of mixed marriages in Corinth, where only one in the couple is a believer. What Paul has to say is significant because a person could argue for divorce on the grounds of irreconcilable differences (and many have). But Paul advises those in a less than desirable marital situation to stay and let God work it out. There are no guarantees that this is going to happen, but it is possible.
LORD, for my friends who are struggling with difficult marriages, please show your power and grace in their circumstances.