1 Corinthians 7:11 (KJV)

But I speak this by permission, and not of commandment.

For I would that all men were even as I myself. But every man hath his proper gift of God, one after this manner, and another after that.

I say therefore to the unmarried and widows, It is good for them if they abide even as I.

But if they cannot contain, let them marry: for it is better to marry than to burn.

And unto the married I command, yet not I, but the Lord, Let not the wife depart from her husband:

But to the rest speak I, not the Lord: If any brother hath a wife that believeth not, and she be pleased to dwell with him, let him not put her away.

And the woman which hath an husband that believeth not, and if he be pleased to dwell with her, let her not leave him.

For the unbelieving husband is sanctified by the wife, and the unbelieving wife is sanctified by the husband: else were your children unclean; but now are they holy.

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.

For what knowest thou, O wife, whether thou shalt save thy husband? or how knowest thou, O man, whether thou shalt save thy wife?