1 Corinthians 7:12-17

12 To the rest I say this (I, not the Lord): If any brother has a wife who is not a believer and she is willing to live with him, he must not divorce her. 

13 And if a woman has a husband who is not a believer and he is willing to live with her, she must not divorce him. 

14 For the unbelieving husband has been sanctified through his wife, and the unbelieving wife has been sanctified through her believing husband. Otherwise your children would be unclean, but as it is, they are holy.

15 But if the unbeliever leaves, let it be so. The brother or the sister is not bound in such circumstances; God has called us to live in peace. 

16 How do you know, wife, whether you will save your husband? Or, how do you know, husband, whether you will save your wife?

17 Nevertheless, each person should live as a believer in whatever situation the Lord has assigned to them, just as God has called them. This is the rule I lay down in all the churches.