‘But as to the rest, I speak, not the Lord. If any brother has an unbelieving wife and she is content to dwell with him, let him not leave her. And the woman who has an unbelieving husband, and he is content to dwell with her, let her not leave her husband. For the unbelieving husband is sanctified in the wife, and the unbelieving wife is sanctified in the brother, otherwise your children would be unclean, but now they are holy.'
‘As to the rest.' He has dealt with their main questions on the subject. Now he will deal with the remainder.
‘I speak, not the Lord.' He acknowledges that in this case he does not have direct words of the Lord to cite or direct evidence from the Scriptures, but nevertheless he speaks as an apostle with spiritual authority, being guided by the Spirit. He has God's seal on what he says. The distinction is made to confirm the stress on the previous ‘not I but the Lord'. It would be apparent that the Lord could not have said this because Jesus spoke in a situation and environment where the question was unlikely to arise.
The principles are simple. The new Christian does not need to seek separation from an unbelieving partner, which they might have considered as necessary in order to cut themselves off from a godless situation in the home and to prevent their continuing to be of one flesh with an unbeliever. This is because their own presence (as temples of the Holy Spirit) ‘sanctifies' the home and those in it. Whatever else this means it means that they do not lose out spiritually by remaining with the unbelieving partner.
Not so simple is the use of the word ‘sanctify'. Here the word ‘sanctified' means that the presence of the Christian in some way makes the other partner come within the sphere of God's earthly, temporal blessing, and under God's temporary protection, and wards off evil spiritual influence. This follows the pattern that whatever touches what is holy becomes holy (Exodus 29:37; Leviticus 6:18). They are not ‘saved', as 1 Corinthians 7:16 emphasises. But they enjoy temporary blessing as being part of a Christian enclave, just as a ‘stranger' dwelling in Israel enjoyed certain benefits while he was there by being under the umbrella of the people of God (Deuteronomy 24:14; Deuteronomy 24:17, 24; Deuteronomy 26:10-13). He enjoyed a peripheral part of the covenant.
In Romans 11:16 Paul can describe all Israelites within the covenant as ‘holy'. They were in a unique position before God, set apart as His people and as such enjoying certain special blessings from God. But the corollary was that more was expected of them. And Paul tells us there that in fact because of their rejection of Christ they had been cut off from their position. But the idea of ‘holiness' as embracing even those who were not fully believing, all through the Old Testament period, is similar to here.
Thus by their conversion the Christian has brought their whole family within the sphere of God's earthly temporary blessing, and especially their children who are seen as in some way enjoying the favourable influence of God. The power of Christ in the Christian neutralises the powers of darkness, and brings positive blessing to the home. Their being the temple of God makes the home ‘holy'.
We can compare to some extent how in Job 1:5 Job ‘sanctifies' his children after they have been feasting by offering sacrifices for them. He returns them within the sphere of God's blessing in case they have forfeited it by sin.
‘Otherwise your children would be unclean, but now they are holy.' The children of non-Christians are indirectly here seen as ‘unclean', that is not within the sphere of God's specific temporal blessings. They are not specifically set apart by God as ‘holy' and set apart to be God's. They enjoy God's general blessings on mankind as a whole, but not His more specific temporal blessings which includes the spiritual influence of a Christian parent. But once a parent becomes a Christian that ‘sanctifies' their children in the sense that they do come within the sphere of God's specific temporal blessing. They are in a privileged position. They come under His cognisance and protection. We would probably understand it better if we knew more about the unseen world and its effects. What matters in respect of Paul's readers is that the believer's children are not put at a disadvantage as far as God is concerned by being in a home where one person is an unbeliever. They come under the same blessing of God as the children of Christian parents, as every Israelite child came within the covenant unless and until they deliberately rejected it. All the blessings of the covenant came to them, but even then eternal salvation depended on genuine response to the covenant.
It should be noted that it is the presence of the Christian parent that produces this effect. We have no real reason to think that it has anything to do with baptising, or otherwise, the children.