“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” (1 Corinthians 7:14).
When I originally did my study on the seventh chapter of Corinthians in 2012, this verse really stuck out to me. I don’t know how I could express my thought better, so I feel a need to quote what I wrote then:
Now Paul makes a remarkable statement that is not repeated anywhere else in any other form. He says that by virtue of the anointing and grace on the believing spouse, their significant other is sanctified (made clean), and so their children will be clean also. Everywhere else, we are taught that it is a personal relationship, that our faith cannot save anyone but ourselves. And even still, we are warned repeatedly of the dangers of such unholy unions (consider Solomon, brought to nought by his many affiliations). By this proclamation, Paul illustrates the exceeding grace God provides in our weakness when we believe (2 Cor 12:9). Because it is harder to keep the faith living in the midst of unbelievers, God has poured out even more grace – to overflowing – to the household of a believer, who converts in the midst of opposition (risking all, their spouse and children) to follow Him. So, though they lose it by forsaking it for God, they gain it back by its sanctification. This grace was not available before Jesus (John 1:17)…
Read more at http://blog.ufuomaee.org/the-marriage-abcs-g