Thank you, my dear friend, for this very important question. Faithful adherence to the Word of God in this and in any other situation is best for everyone concerned. So, what is the overriding principle regarding marriage that we find in the Scriptures? In 1 Corinthians 7:10-11 we read: “And unto the married I command, yet not I, but the Lord, Let not the wife depart from her husband: But and if she depart, let her remain unmarried or be reconciled to her husband: and let not the husband put away his wife.” You can see from these verses that once married, the Bible does not condone divorce and remarriage, except for the possible situation of unfaithfulness (Matthew 19:9). As well, the Scripture does not condone for a Christian to marry an unbeliever (2 Corinthians 6:14).

But now, I believe that your question relates to the guidance given in 1 Corinthians 7:12-17 very specifically. So, let’s look at verses 12-13: “But to the rest speak I, not the Lord: If any brother hath a wife that believeth not, and she be pleased to dwell with him, let him not put her away. And the woman which hath an husband that believeth not, and if he be pleased to dwell with her, let her not leave him.” I want to begin by addressing the first phrase in verse 12. When Paul says, “But to the rest speak I, not the Lord…”, there is absolutely no thought that this guidance is only Paul’s opinion rather than the Lord’s will.  The Bible as a whole is the Word of God and is good for all instruction in righteousness (2 Timothy 3:16-17). What is meant here, I believe, is that Paul is expressing a truth that the Lord Jesus did not specifically address while on the earth, but it is the Will of God none-the-less.

Thus, these two verses respond directly to your question and represent the will of God when two people marry, then later one of them becomes a believer while the other does not. They should remain together as husband and wife so long as the unbeliever is pleased to remain in the relationship. The believer is not to separate from or divorce the other simply because the other is yet an unbeliever. Now, there could be reasons where a separation might be anticipated, such as infidelity (Matthew 19:9), and I’m sure there might be other reasons, such as health or safety issues, where a separation might be considered; but not just because the other is not yet saved. And why is this? Verse 14 states “For the unbelieving husband is sanctified by the wife, and the unbelieving wife is sanctified by the husband: else were your children unclean; but now are they holy.” I will try to explain these verses. The reason not to part from an unbelieving spouse is two-fold. First, there is every possibility that through the continued marriage relationship, the unbelieving spouse might be saved (1 Corinthians 7:16). We must not underestimate the spiritual effect on the unbeliever of a believer living a godly life before the unsaved.  Many a spouse has been saved by seeing the love and faithfulness of their believing spouse, seeing the impact of the Spirit of God and His Word on the believer. Certainly, the believing partner should walk a holy walk before the unbelieving spouse and any children as this is the best testimony of the truth and power of God in the life of a believer. But in any case, they are to remain together so long as the unbeliever is content to remain. The second consideration for remaining together so long as the unbelieving spouse is willing to remain is that the relationship is “sanctified” in the eyes of God, and the children are considered “holy”.  This means that the marriage itself is accepted by the Lord as legitimate, and so also are any children of that marriage.  It does not mean that the unbelieving spouse and/or children are automatically saved, but only that the relationship is not a sin. Finally, verse 15 covers the issue if that unbeliever is not content to remain in the relationship “But if the unbelieving depart, let him depart. A brother or a sister is not under bondage in such cases: but God hath called us to peace.” Thus, if the unbelieving spouse is not content to remain in the marriage relationship with the believer, the Word of God tells us that she/he should be allowed to depart, and the believer should not try to forcibly block the departure of the unbeliever. (SF)  (617.3)