“Now, I will speak to the rest of you, though I do not have a direct command from the Lord. If a fellow believer has a wife who is not a believer and she is willing to continue living with him, he must not leave her. And if a believing woman has a husband who is not a believer and he is willing to continue living with her, she must not leave him. For the believing wife brings holiness to her marriage, and the believing husband brings holiness to his marriage. Otherwise, your children would not be holy, but now they are holy. (But if the husband or wife who isn’t a believer insists on leaving, let them go. In such cases the believing husband or wife is no longer bound to the other, for God has called you to live in peace.) Don’t you wives realize that your husbands might be saved because of you? And don’t you husbands realize that your wives might be saved because of you?” 1 Corinthians 7:12-16
This scripture deals with the marriage of believers and unbelievers. On this Paul has to give his own judgment, because there is no definite command of Jesus to which he can refer them. The background must be that there were those in Corinth who declared that a believer must never live with an unbeliever; and that, in the event of one partner of a marriage becoming a Christian and the other remaining a heathen, separation must at once follow. In fact, one of the great heathen complaints against Christianity was exactly that Christianity did break up families and was a disruptive influence in society.
Paul dealt with this problem with supreme practical wisdom. He knew the difficulty and he refused to make the problem worst. He said that if the two could agree to live together by all means let them do so; but if they wished to separate and found living together intolerable, let them do so, because the Christian was never meant to be a slave.
There is value in Christians living with unbelievers. The unbelieving partner is consecrated by the believer. The two have become one flesh and the wonder is that in such a case it is not the taint of heathenism but the grace of Christianity which wins the victory. There is an infection about Christianity which involves all those who come into contact with it. A child born into a Christian home, even into a home where only one of the partners is a Christian, is born into the family of Christ. In a partnership between a believer and an unbeliever, it is not so much that the believer is brought into contact with the realm of sin, as that the unbeliever is brought into contact with the realm of grace. The Christian can also lead to the saving of the unbeliever.