1 Corinthians 7:1-16 (ESV)
Principles for Marriage
7:1 Now concerning the matters about which you wrote: “It is good for a man not to have sexual relations with a woman.” 2 But because of the temptation to sexual immorality, each man should have his own wife and each woman her own husband. 3 The husband should give to his wife her conjugal rights, and likewise the wife to her husband. 4 For the wife does not have authority over her own body, but the husband does. Likewise the husband does not have authority over his own body, but the wife does. 5 Do not deprive one another, except perhaps by agreement for a limited time, that you may devote yourselves to prayer; but then come together again, so that Satan may not tempt you because of your lack of self-control.
6 Now as a concession, not a command, I say this.  7 I wish that all were as I myself am. But each has his own gift from God, one of one kind and one of another.
8 To the unmarried and the widows I say that it is good for them to remain single as I am. 9 But if they cannot exercise self-control, they should marry. For it is better to marry than to burn with passion.
10 To the married I give this charge (not I, but the Lord): the wife should not separate from her husband 11 (but if she does, she should remain unmarried or else be reconciled to her husband), and the husband should not divorce his wife.
12 To the rest I say (I, not the Lord) that if any brother has a wife who is an unbeliever, and she consents to live with him, he should not divorce her. 13 If any woman has a husband who is an unbeliever, and he consents to live with her, she should not divorce him. 14 For the unbelieving husband is made holy because of his wife, and the unbelieving wife is made holy because of her husband. Otherwise your children would be unclean, but as it is, they are holy. 15 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. 16 For how do you know, wife, whether you will save your husband? Or how do you know, husband, whether you will save your wife?