What counts as adultery in the Bible?

This was forbidden in the ten commandments; but neither there nor anywhere else is the sin defined. It seems clear, that as far as the man was concerned, if he had intercourse with a woman unless it was with a married woman, he would not be charged with adultery, though he himself might be married; indeed how could he be when he was allowed more wives than one, as well as concubines and slaves? If he committed adultery with a married woman or with one betrothed, both were to be put to death. Deut. 22:22-24. With the woman it was stricter, she must have no intercourse with any man but her husband. If a man was jealous of his wife there was the ordeal of the bitter waters provided to test her innocence. Num. 5:11-31. But we do not read that any man or woman was stoned for adultery, nor that any woman drank the bitter waters. We know from the New Testament that Moses had, because of the hardness of their hearts, allowed a certain looseness, and a man could divorce his wife for any cause, which was easier than bringing a suspected wife to trial. It may be that the men themselves had not good consciences, like those who brought the adulterous woman to the Lord in John 8:3. We have a dreadful picture of guiltiness in Judges 19: and Jeremiah charges Israel with being "as fed horses in the morning, every one neighed after his neighbour's wife," which loudly called for judgement. Jer. 5:8; Jer. 13:27. The Lord declared that a man morally committed adultery (or fornication) in his heart if he lusted after a woman. Adultery had also a typical meaning. Israel had been espoused to Jehovah, but instead of being a faithful wife she had sought other lovers. "With their idols have they committed adultery." Ezek. 23:37. So the false church, who has Jezebel in her midst, the Lord will cast her "and them that commit adultery with her into great tribulation, except they repent of their deeds." Rev. 2:22.

The seventh commandment safeguards the purity of human life. "Adultery" here has the widest sense, covering what are considered to be lesser forms of this sin between the sexes. The history of peoples shows those who have widely practised this evil have degraded themselves both physically and mentally, and out of it spring a host of other ills.

The Lord Jesus now explains that before God it is not just the accomplished act that is sin, but the looking with lust on a woman, for this is adultery in the heart. The word "adultery" shows that either the man or both are married. Nevertheless, no unmarried believer should think that these words of the Lord have nothing to say to him.

The whole of Scripture is full of the errors of fornication (Acts 15 v 29) and adultery (Exodus 20 v 14). The first is sexual relationship outside of marriage and the second sexual relationship with a married person. We must clearly state that physical affection is only intended by God for one man and one woman and that within the confines of marriage and to a very limited extent by a couple committed to marriage (see previous chapter).

Therefore, confirming what was implicit in creation, the Lord adds, "And I say unto you, Whosoever shall put away his wife, except it be for fornication, and shall marry another, committeth adultery: and who so marrieth her which is put away doth commit adultery." The one exception allowed here is because the marriage bond has been so violated as to be virtually broken already. If the one party is guilty of fornication, then it would not be adultery for the other party to divorce the first and marry another. But the one who married the party put away for fornication would be guilty of adultery.

Matthew 19:1-9 must be studied with the words of Moses on divorce. The Pharisees asked the Lord "why did Moses then command to give a writing of divorcement, and to put her away?" But they erred when they called Moses' word a commandment. It was only something which Moses allowed. Adultery according to the law was punishable with death. "He saith unto them, Moses, because of the hardness of your hearts, suffered you to put away your wives; but from the beginning it was not so. And I say unto you, Whosoever shall put away his wife except it be for fornication, and shall marry another, committeth adultery; and whosoever marrieth her that is put away doth commit adultery."

For that reason the Lord now says, "But I say unto you, That whosoever looketh on a woman to lust after her, hath committed adultery with her already in his heart" (v. 28). Because of the teaching of the scribes and Pharisees, the Jews thought the mere outward observance of the law was the way to be justified before God. Here, the Lord points to the human heart and shows that adultery has its source there. This is not a "spiritualisation of the law," as is sometimes said. He reveals for the first time something which had to become clear by experience to every honest Israelite, namely, that everyone who endeavoured to keep the commandment, "Thou shalt not commit adultery," had within themselves those very lusts which led to the actions forbidden by God, and had not the strength to overcome them. The lusts were even provoked by the commandment: "... for I had not known lust, except the law had said, Thou shalt not covet" (Rom. 7: 7-11).

In the Old Testament, adultery, unfaithfulness towards the spouse for the satisfaction of lust, was to be dealt with most severely. According to the law of Sinai this sin had to be punished with death (Lev. 20: 10; Deut. 22: 22-24). In the first place the law contained God's regulations for the outward and social life of His earthly people, and for this reason only the accomplished offence was to be punished, even though the tenth commandment forbad the coveting of the neighbour's wife (as well as all his possessions. Ex. 20: 17). If a Jew kept the commandment not to commit adultery, he was acting according to God's will and contributed towards the maintenance of the people's community according to God's order. Fear of the punishment threatened certainly contributed to this. However, the mere outward observance of this and all the other commandments could not justify him before God.

Adultery too (a guilty infraction of the marriage bond) called for the death penalty for both the man and the woman involved in this. God does not require Gentile governments to enforce Israel's laws, but these evils are no less wicked wherever they are found. Meanwhile, God is delaying punishment, and today is commanding all people everywhere to repent (Acts 17:30). If so, they will be saved from the punishment they deserve: if not, their punishment will be not only death, but eternal torment in the lake of fire.

In the case of a man committing adultery with a woman married to a husband, both the guilty man and the woman were to be put to death (v.22). This is justice. If such a sentence were carried out today, how many people would die! But too many people, taking advantage of God's patient grace, think they can get away with much evil. What a shock it will be for many who have not actually received the .grace of God by faith, when they find themselves faced before God with all the evils they have so lightly practiced!