The Bible alone establishes the rules for marriage and one of the most important is that a believer must not marry an unbeliever.

To Israel, in Old Testament times, the following command was given with respect to the unconverted nations: ‘Neither shalt thou make marriages with them: thy daughter thou shalt not give unto his son, nor his daughter shalt thou take unto thy son’ (Deut. 7:3, cf. Gen. 24:3; 28:1, 2; Josh. 23:12, 13). This is a definite prohibition of mixed marriages. However, if foreigners were converted to the worship of the true God, it would seem that marriage was allowed. The law of Moses permitted an Israelite to marry a female prisoner of war, provided that she became a Jewish convert and submitted to the customary purification rites (Deut. 21:10-13; cf. Lev. 14:8; Num. 8:7). We also have, of course, the example of Rahab the Canaanite and Ruth the Moabitess, both of whom were converted and subsequently married to Israelites (Josh. 2:9, 11; 6:25; Ruth 2:11, 12; 4:9, 11; Mt. 1:5). The prohibition was therefore not so much against marrying Gentiles as against marrying unbelieving Gentiles.

In the New Testament the commands concerning marriage are just as explicit. Paul lays down the basic principle in 2 Corinthians 6:14, 15: ‘Be ye not (or, ‘Become ye not’) unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? And what concord hath Christ with Belial?’ The reference is to Deuteronomy 22:10 which forbids any ploughing with an ox and an ass together. These animals were not only different in size and strength, but according to the law given in Deuteronomy 14:1-8, the ox was ‘clean’ but the ass was ‘unclean’. Paul applies this Mosaic law to human life. It is quite wrong, he says, to enter into close relationships with unbelieving people. It will prove ‘an unequal yoke’ and can only lead to friction and distress, a pulling in different and even opposite directions, and at the end of the day nothing really worthwhile will have been accomplished. In another place, Paul deals with the matter somewhat more positively. He gives some basic teaching on marriage and asserts that marriage should last until death. He then says that when one party dies, the other is free to marry anyone he or she chooses – ‘only in the Lord’ (1 Cor. 7:39). In other words, the person must be in fellowship with Jesus Christ. Paul is insisting that believers marry believers, and none but believers.

There are some further considerations:

1. The Unity of Marriage⤒🔗

First of all, God’s ideal for marriage is a close and intimate union which is expressed physically, but actually involves oneness of thought, desire and purpose (Gen. 2:23, 24). Quite obviously, if the two people getting married have nothing spiritually in common, they cannot achieve total union and complete oneness. As Paul says, ‘What fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?’ (2 Cor. 6:14). To marry an unbeliever is to forfeit God’s best.

2. The Compromise of Intermarriage←⤒🔗

Secondly, intermarriage with unconverted people invariably results in a life of sinful compromise. ‘Be not deceived: evil communications (or, bad companionships) corrupt good manners’ (1 Cor. 15:33; cf. Prov. 13:20). God repeatedly warned the Israelites about this (e.g. Ex. 34:16) and, in Scripture, Solomon is set forth as a terrible warning to us. ‘King Solomon loved many strange (i.e. foreign) women ... and his wives turned away his heart ... and his heart was not perfect with the Lord his God, as was the heart of David his father’ (1 Kings 11:1-4; cf. 21:25; 2 Kings 8:18; and Judg. 3:5-7; Ps. 106:35). Such marriages are slippery slopes to sin and, in some cases, even to apostasy.

3. The Impact on Children←⤒🔗

Thirdly, mixed marriages are also sources of evil to the children. When one parent is utterly estranged from God and ignorant of his Word, there cannot be proper family government and worship, and so we cannot really expect to find ‘a godly seed’ (Mal. 2:15). Genesis 6 describes how, early in history, ‘the sons of God’ (believers, Hos. 1:10, Jn. 1:12, the descendants of Seth) began to marry ‘the daughters of men’ (unbelievers, Ps. 4:2, 57:4, Jn. 3:6, of the Cainite line). The result was a whole generation of ungodly people. ‘There were giants in the earth in those days’ (v. 4). The word translated “giants”, as Dr. Henry Cooke observes, ‘is derived from a root that signifies to ‘fall’ or ‘fall upon’; and conveys the idea of apostasy from true religion, and violent invasion of others’ rights and properties – apostate persecutors and tyrants’. Those tempted to be disobedient should take account of these things, and think of the effect their contemplated action will have upon their unborn children.

4. The Impact on the Church←⤒🔗

Fourthly, we must understand too that mixed marriages greatly hinder the professing church. In appointing marriage, God intended that man should have ‘an help meet for him’ or, as more literally translated, ‘an help before him’ i.e. one corresponding to him and very much like him (Gen. 2:18). Notice that the woman was not only to be perfectly suitable but also a helper with him in the fulfilling of God’s will (cf. 1:28). A real Christian marriage makes that a wonderful possibility. We may think, for example, of Priscilla and Aquila whom Paul once described as ‘my helpers in Christ Jesus’ (Rom. 16:3; cf. Acts 18:26; 1 Cor. 16:19). In a mixed marriage, on the other hand, even if the believing partner continues in the faith, without sympathy and support in the home, he or she will find it very difficult, and at times quite impossible, to help forward the Lord’s work in the church. It is a dreadful thing to be like David and have a Michal at our side who seeks to dampen our zeal and hinder our service to the house of God (2 Sam. 6:16).

5. ​The Damage to the Testimony←⤒🔗

Fifthly, marriage to the unconverted tends only to destroy the Christian’s testimony. Whatever the witness in the past, this blatant disregard of God’s Word can only bring reproach upon the Lord’s name and cause (cf. Rom. 2:24; Titus 2:5; 2 Pet. 2:2). The Bible declares how, centuries after his death, Solomon is remembered not so much for his religious profession as for his sin in contracting marriages with ungodly women. ‘Did not Solomon king of Israel sin by these things? yet among many nations was there no king like him, who was beloved of his God, and God made him king over all Israel: nevertheless even him did outlandish women (i.e. of another country, nation and religion) cause to sin’ (Neh. 13:26).

​6. The Grief to God's People←⤒🔗

Sixthly, in marrying outside the faith a Christian brings grief to godly parents and indeed to all the Lord’s people. When Esau, at the age of forty, took as wives two unconverted Canaanite women, Scripture says it was ‘a grief of mind (or, more literally, ‘a bitterness of spirit’) unto Isaac and Rebekah’ (Gen. 26:35; cf. 27:46). Similarly, Ezra, the priest and scribe, demonstrated intense concern on discovering that certain Jews had been unfaithful in this matter. ‘When I heard this thing’, he says, ‘I rent my garment and my mantle, and plucked off the hair of my head and of my beard, and sat down astonied (i.e. horrified)’ (Ezra 9:3). Believing Jews understood what it meant. Godly lives were being ruined. Dreadful examples were being set to others. The Lord was being denied the glory due to His holy name.

7. The Sin Involved←⤒🔗

Seventhly, contracting such marriages is sin and, according to the Bible, great sin, because it is committed in the face of emphatic prohibition (Ezra 9:14, 15; Neh. 13:26, 27). And the greater the sin, the greater will be the judgment. Ezra felt this keenly as, on behalf of his people, he acknowledged their guilt and implored God for pardon. ‘Should we again break thy commandments, and join in affinity with the people of these abominations? wouldest not thou be angry with us till thou hadst consumed us, so that there should be no remnant nor escaping?’ (Ezra 9:14). His question was never answered. In this way God impresses upon us how evil a thing it is. Let his people therefore resolve never to transgress this holy commandment.

This teaching has always been accepted as biblical and true among evangelical and reformed Christians. John Calvin was in no doubt about it and referred to mixed marriage as ‘a snare by which both men and women are entangled into an agreement with impiety’. In a letter to a friend, he asked: ‘How can you expect a good wife from Him whom you will not hear while strictly prohibiting you from being “yoked with unbelievers”?’ The Puritans agreed. Thomas Adams said in one of his sermons: ‘No man can choose a worse friend than one whom God holds his enemy’. Henry Smith issued a similar warning, and then exclaimed: ‘What a monstrous thing it is for believers and unbelievers to match together!’ The early Non-Conformists were militant in their opposition. When the subject was raised at the General Assembly of Baptists in 1689, it was discussed at some length, and then this statement was issued: ‘It is unlawful for a believer to marry with a non­believer’. And the same holds good for all professors, whatever their denomination may be.

This article, of course, is mainly intended for the single and the unmarried. If Christians, for some reason, find themselves already in marriages with non-Christians, they should remain with their partners, doing all they can to help them to faith in our Lord Jesus Christ (1 Cor. 7:12-16; 1 Pet. 3:1, 2). God honours consistent testimony and answers sincere and fervent prayer. But for the others, in the matter of ‘the unequal yoke’, the Lord grant his people the grace both to honour and to obey him!