Is it wrong for a Christian to have a sexual fantasy?

Adultery in the heart

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 Lord is not speaking here about accidental, unintentional looks which can hardly be avoided, but about the conscious covetous looking: “Whosoever looketh on a woman to lust after her … ” The intentional look is therefore preceded by the sinful thought in the heart.

This distinction is very important. Nowadays we can hardly move in this world without, unintentionally, continually witnessing the moral depravity of our time. We are easily defiled by this. The intentional covetous and sinful look is something completely different. No Christian can avoid unclean thoughts rising up in his mind but they only become sin when instead of turning away from them he consciously gives himself to them. If covetous looks and unclean lines of thought are sin, then it is also sin if believing women and girls cause and provoke this by their dress and behaviour.

Adultery in the heart

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 Lord is not speaking here about accidental, unintentional looks which can hardly be avoided, but about the conscious covetous looking: "Whosoever looketh on a woman to lust after her..." The intentional look is therefore preceded by the sinful thought in the heart.

This distinction is very important. Nowadays we can hardly move in this world without, unintentionally, continually witnessing the moral depravity of our time. We are easily defiled by this. The intentional covetous and sinful look is something completely different. No Christian can avoid unclean thoughts rising up in his mind but they only become sin when instead of turning away from them he consciously gives himself to them. If covetous looks and unclean lines of thought are sin, then it is also sin if believing women and girls cause and provoke this by their dress and behaviour.

Let one instance suffice out of the seven occasions in that discourse when our Lord said, “I say to you.” “Ye have heard that it was said of them of old time, Thou shalt not commit adultery: but I say to you, That whosoever looks on a woman to lust after her has committed adultery with her already in his heart” (Matt. 5:27-28). Where is there the setting aside of the law? Nay, He upheld it. The law was content to forbid the actual act, the Lord went further, and not only forbad the outward act, but the inward desire.

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).

The more casual and free contact between the sexes, especially with the younger generation and the negative example of most of their peers of the world, can lead to carelessness and great dangers. God-fearing Job said: "I made a covenant with mine eyes; why then should I think upon a maid?" (Job 31: 1). However, there are also over-sensitive and over-anxious Christians whose consciences are heavily burdened by involuntary looks and thoughts. I would like to remind such of the well-known words of Martin Luther which he wrote on this verse: "I cannot prevent a bird flying over my head, but what I can prevent is it building a nest in my hair or biting off my nose."

Some of us were speaking about the Sermon on the Mount as found in Matthew 5-7. We noticed how the Lord puts His hand on the desires of the heart. It is not sufficient to have strength not to commit the sins of the flesh, but the desire of the heart, as the flesh works, must not be encouraged. Though shame would forbid the outward acts of the flesh, yet if carnal desires are cherished in any way, then the Lord looks upon that as gravely as if the act were committed.

Lasciviousness. The indulgence of impure subjects in the imagination promotes the performance of corresponding acts of impurity.

It is sometimes said that deliverance from sin is a matter of personal effort, and that evil habits can and should be overcome by one's own firm resolution and perseverance. But this advice overlooks the fact that although the wicked deed may be checked by will-power alone, the sinful desire fills the heart beforehand. And divine holiness uncovers the secret source of inward evil. In God's sight, the thought of foolishness is sin. Our Lord condemns alike the lustful look and the adulterous act (Matt. 5:28). The evil thought defiles the whole man, as well as the evil word and the evil act (Mark 7:21-23). We should habitually govern our words and our deeds, but who can govern the imagination of the heart which God beholds? If we are walking with God, we are with One Who knows our thoughts even before we recognise them ourselves. The holiness of God is very pure, infinitely above any human standard, and in order to act rightly with regard to that standard, we must attend to the words of scripture concerning the “sin which doth so easily beset us.”

As violence then was judged and excluded in any shape for the disciples, so was impurity. The avoidance of the extreme act might satisfy a Pharisee or Scribe; but the Lord could not dispense with anything short of truth in the inward parts. To look at a woman lustfully was to commit adultery with her already in his heart; and it is not the outside only that God regards but the heart above all. It is only a new nature that delights in holiness; and he who has it by grace answers to the will of God his Father; and abhors himself if he slip even into a wrong look, as unworthy of his calling and hateful to Him who loves him.

But there is another thing besides violence: there is the corrupt element in the heart of man — the heart lusting for that which it has not. This is taken up in the next word of our Lord: "Ye have heard that it was said by them of old time, Thou shalt not commit adultery: but I say unto you, that whosoever looketh on a woman to lust after her, hath committed adultery with her already in his heart. And if thy right eye offend thee, pluck it out and cast it from thee … And if thy right hand offend thee, cut it off, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell" (vers. 27-30). That is, whatever in our walk, or in our ways, or in our service, whatever it might be that exposes a soul to the danger of yielding to these unholy feelings, should never be spared, but departed from at any cost. There must be the excision of everything that is hurtful to the soul; the members of the body, such as the eye desiring and the hand which would take, being used as showing the various ways in which the heart might be entangled. The cutting off of these members sets forth a heart thoroughly exercised in self-judgment; not prompted to excuse itself by saying that it had not actually committed the sin, but whatever exposed to it must be given up.