“ For how knowest thou, O wife, whether thou shalt save thy husband? Or how knowest thou, O man, whether thou shalt save thy wife?”
[1 Corinthians 7:16]
What is v16 saying? What does it mean? Why is it here? Is it unnecessary or does it clarify the previous verses?
v15 is the fundamental, scriptural authority for the doctrine called the Pauline Privilege (PP) - not to be confused with another Church doctrine called the Petrine Privilege - but then v16 is in opposition to the PP. So I’d like to see if anyone has a good, thoughtful explanation for v16 in the context of this part of scripture.
Context (DR): Instruction to Christians about marriage, about divorce and about remarriage.
But I speak this by indulgence, not by commandment.  For I would that all men were even as myself: but every one hath his proper gift from God; one after this manner, and another after that.
But I say to the unmarried, and to the widows: It is good for them if they so continue, even as I.
 But if they do not contain themselves, let them marry. For it is better to marry than to be burnt.
 But to them that are married, not I but the Lord commandeth, that the wife depart not from her husband.
 And if she depart, that she remain unmarried, or be reconciled to her husband. And let not the husband put away his wife.
 For to the rest I speak, not the Lord. If any brother hath a wife that believeth not, and she consent to dwell with him, let him not put her away.
 And if any woman hath a husband that believeth not, and he consent to dwell with her, let her not put away her husband.
 For the unbelieving husband is sanctified by the believing wife; and the unbelieving wife is sanctified by the believing husband: otherwise your children should be unclean; but now they are holy.
 But if the unbeliever depart, let him depart. For a brother or sister is not under servitude in such cases. But God hath called us in peace.
 For how knowest thou, O wife, whether thou shalt save thy husband? Or how knowest thou, O man, whether thou shalt save thy wife?
If the act of letting the non-Christian husband (or wife) leave unbinds the Christian from their marriage is part of some plan to ‘save’ the non-Christian, then the sentiments expressed earlier, all of which are oriented towards the couple remaining in a marital relationship, even with an non-Christian, would rather support the idea that the abandoned spouse should wait for their non-believing spouse to be saved and return, have their marriage canonically validated in the Church and therefor have the full Sacrament of Matrimony. And NOT have the Christian divorce their spouse to ‘marry’ someone else?
If you take out v16, the PP would be better supported. But v16 is there. Hence my inquiry of others as to their thoughts about why its there, what it means especially how it explains v15.