Sanctification in 1 Corinthians 7:14

Here is a spot of Alan Conner discussing holy in 1 Corinthians 7:14.

It is true that the children of a believing parents are holy. But what does this mean? Since the unbelieving spouse is also "sanctified" (same word as "holy" used for the children only its verbal form), it seems only logical that they will be holy in the same way that the children are holy. No one in their right mind would assert that the unbelieving spouse is a member of the New Covenant. Neither should anybody think that the unbelieving spouse is worthy of being baptised. To baptise an unbeliever would make a mockery of the gospel which requires faith for salvation. But if both the unbelieving spouse and children are sanctified and made holy the the believing spouse and parent, why do some argue that the children are members of the covenant and should be baptised, but not he unbelieving spouse? And why do some insist on calling the children "saints" (holy ones), but not the unbelieving parent? Since both are made holy by the believer, to make one a holy covenant member and not he other, and to baptise one and not he other is an inconsistency which renders this view point completely unacceptable. Whatever this sanctification means, it cannot be used to argue for the paedobaptist view of "covenant children" which sanctions the baptism of infants or else, one must also argue for "covenant unbelieveing spouses" and the baptism of unbelievers.

How then are we to explain the sanctification in this verse? We could take it in a similar way to Hebrews 10:29 and understand that both the unbelieving spouse and he the children of believers are made holy or sanctified outwardly in some sense by the godly influences of the believer. But this verse states the sanctification of the unbelieving spouse and children as a fact, and yet this may not always be the case if it only refers to some kind of moral influence brought to bear upon them by the believer.

A better solution is to see this sanctification as referring to their being conformed to God's moral law so that the marriage and family unit are morally sound and holy in the sight of God. In other words, the marriage and family are legitimate and lawful, even though one spouse is still an unbeliever. Their unbelief does not make the marriage void or invalid.

One cannot help but think of a similar situation in Ezra chapters 9 and 10 in which the Israelites had married the daughters of the Canaanites. Such mixed marriages were looked upon as an abomination and the Israelites had to put away all of their foreign wives and their children (Ezra 10:3). If the Corinthian believers were aware of this, as the Jewish believers no doubt were, we could understand their concern about their own mixed marriages to unbelievers. "Is my marriage to an unbeliever and abomination? Should I put them away like God commanded the Israelites in the days of Ezra? What about my children, are they an abomination too?" These thoughts could easily be in the background of these verses to the Corinthian church.

What, then, is Paul's answer? In essence it is this - both your marriage and your children are legitimate before the Lord. They are holy and not to be discarded even though your spouse is an unbeliever and your children are descended from him (or her) as well as from you. The situation with Ezra was a different time and a different set of circumstances. Your children are not illegitimate because your marriage to the unbeliever is a lawful marriage and conforms to Gods' will.

Thus, the sanctification found in 1 Corinthians 7:14 cannot be made to argue that he children of believers are covenantally holy and therefore should be baptised as infants.....

Covenant Children Today by Alan Conner pp. 98-99