1 Corinthians 7:14

For the unbelieving husband is set apart (separated, withdrawn from heathen contamination, and affiliated with the Christian people) by union with his consecrated (set-apart) wife, and the unbelieving wife is set apart and separated through union with her consecrated husband. Otherwise your children would be unclean (unblessed heathen, outside the Christian covenant), but as it is they are prepared for God [pure and clean].