1 Coríntios 7

12 Now, to the rest of you (and this is me speaking, not the Lord), I would say, If a Christian man has a non-Christian wife and she is willing to stay with him, he should not leave her. 13 And if a Christian woman has a non-Christian husband, and he is willing to stay with her, she should not leave her husband.

14 For a husband who is not a Christian, the marriage relationship is made holy by the Christian wife, and for a wife who is not a Christian, the marriage relationship is made holy by the Christian husband.*7:14. Paul is not saying here that being married to a Christian the non-Christian spouse therefore becomes a Christian or experiences salvation. He is concerned to address the issue that by being married to a non-Christian spouse in some way "defiles" the marriage or the Christian in the relationship. That this is the real issue is made clear concerning children of such a marriage—they are also not "impure" but they are "holy," and this is not any reference to the actual spiritual state of the children. Otherwise it would mean your children were impure, but now they are holy.