1 Corinthians 7:10-11, 15

To the married I give this charge (not I, but the Lord): the wife should not separate from her husband (but if she does, she should remain unmarried or else be reconciled to her husband), and the husband should not divorce his wife.

But if the unbelieving partner separates, let it be so. In such cases the brother or sister is not enslaved. God has called you to peace.