Paul’s word in the New Testament is clear enough. In 1 Corinthians 7:39, he told the widows to marry those who were in the Lord.
Second Corinthians 6:14 is a well-known portion of the Bible. It says that believers and unbelievers should not share the same yoke. These words do not refer to only marriage. But they certainly speak also of marriage. Believers and unbelievers should not be engaged in the same business; they should not join themselves in one goal, like two animals plowing the field with one yoke. God does not allow this. He does not allow a believer and an unbeliever to bear the same yoke. In the Old Testament, an ox and a horse could not be yoked together, and an ass could not be equally yoked with a horse. You cannot have one that is fast and another that is slow. It is impossible to have one going one direction and the other going another direction, or one turning to heaven and the other turning to the world. You cannot have one seeking after spiritual blessings and the other seeking after worldly riches. It is impossible for one to pull in one direction and the other to pull in the other direction. If you do, the yoke will break.
Of all unequally yoked relationships, none is more serious than the marriage relationship. One may be unequally yoked with others in business ventures or in other things. But no yoke is more severe than the marriage yoke. When a believer and an unbeliever share the responsibility of a family together, the result will be nothing but problems. The ideal marriage partner is a brother or a sister. Never choose an unbeliever capriciously. If you pick out an unbeliever carelessly, you will surely encounter problems later. One will be pulling to one side, and the other will be pulling to the other side. One will turn to heaven, and the other will turn to the world. One will seek a heavenly gift, and the other will seek worldly riches. The difference between the two is tremendous. This is why the Bible charges us to marry those in the Lord.
But here is a problem: Suppose a brother is already married to an unbeliever, or a sister is already married to an unbelieving husband. What should they do? We mentioned earlier that a single person should seek a partner who is in the Lord. However, there are some who are already married. They already have an unbelieving wife or an unbelieving husband. What should they do?
First Corinthians 7 has something to say about this matter. Verses 12, 13, and 15 address this point. They tell us what to do when a dispute arises in a family that has only one member who is a Christian. Please bear in mind that many such families today complain little, simply because the believers in these families are not absolute enough. The Lord Jesus predicted in the Gospels that there would be much contention within the family. If a believer is absolute, there is bound to be contention in the family. There are cases of “three against two and two against three,” as in Luke 12:52, because some family members have become believers. Suppose a husband leaves his wife because she has believed in the Lord. Suppose he says, “You have believed in the Lord; I do not want you anymore.” What should the wife do? The Lord’s word in 1 Corinthians 7 is clear enough: “Let him separate” (v. 15). Therefore, if a husband wants to separate because the wife has believed in the Lord, or vice versa, the word is, “Let him separate.”
However, one thing must be clear: You must not be the one who initiates the separation. You must not be the one who asks for the separation. The other party must be the one who asks for it. He is the one who is not happy with your faith in the Lord. He is the one who thinks that there is no future with you now that you have believed in the Lord. It is he who wants to go. If he wants to separate, “Let him separate.”