2 Corinthians 6:14
Do not team up with unbelievers [i.e., in close relationships, such as marriage, etc.]. For what do righteousness and wickedness have in common? Or, what fellowship can light have with darkness?
1 Corinthians 7:14
For the unbelieving husband is set apart [i.e., as an acceptable mate, although not yet saved. See verse 16], through his wife [i.e., her Christian commitment is viewed as having a godly effect on the home], and the unbelieving wife is set apart through the brother [i.e., for the same reason]. Otherwise, your children would be [considered] unclean. [Note: "Unclean" suggests they would be viewed as pagans were it not for one parent being a Christian]. But, as it is, they are set apart as acceptable [i.e., to God, because of the influence of the one Christian parent].