Charles Ellicott Commentary 1 Corinthians 7:14

"For the unbelieving husband is sanctified in the wife, and the unbelieving wife is sanctified in the brother: else were your children unclean; but now are they holy." — 1 Corinthians 7:14 (ASV)

The unbelieving husband is sanctified by the wife.—Any scruple a Christian might have felt about whether marriage to an unbeliever would be defiling is removed here, and the purity of the former teaching is justified. In contrast to that other union where the connection is defiling (1 Corinthians 6:16), the purity of the believing partner in this lawful union, so to speak, entirely outweighs the impurity of the unbeliever, this impurity being not moral, but a kind of ceremonial impurity.

The children of such marriages were considered Christian children; and since the fruit is holy, so we must also regard as holy the tree from which it springs. It must be remembered that the “sanctification” and “holiness” spoken of here is not that inward sanctification which springs from the Holy Spirit’s action in the individual heart, but rather that consecration which arises from being in the body of Christ, the Christian Church (Romans 9:16).