Is it wrong to have a fantasy, according to the Bible?

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.

It is not the first step that leads to a public fall. There must be the secret encouragement before things get to the point of open scandal. In the Sermon on the Mount it is “the PURE in heart” that will see God. It is well to be exercised about the thoughts of the heart, for if they are kept in captivity to the Lord actions will be right. Spurgeon said, “You cannot forbid unclean birds flying over your head, but you can hinder their making a nest in your hair.”

Thoughts unbidden come into the mind that clearly are not of the Spirit of God, but of the flesh. We need not trouble about them, unless we are so foolish as to willingly give them a lodging place in our hearts. The wise man knew full well where the citadel of life is situated, when he wrote to his son, “Keep thy HEART with all diligence; for out of it are the issues of life” (Prov. 4:23).

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.

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.

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.

The next two expansions of the law are concerning purity and divorce. Not alone the deed itself, which was punishable by a severe penalty, is sin, but every one who looks upon a woman to lust after her has already committed adultery with her in his heart. Out of the heart the transgression comes, and the heart is evil. And this is what so many persons in Christendom say is their creed and standard for "religion"! It is the word which condemns them altogether.

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.

As to the two commandments He quoted, His teaching evidently is that God has respect not only to the overt act but also to the inward disposition of the heart. What is prohibited is not merely the act of murder or adultery but the hatred and the lust of which the act is the expression. Judged by this standard, who is going to stand before the holy demands of Sinai? The "righteousness" of the scribe and Pharisee utterly collapses. Yet in both cases, having exposed this fact, He added some further instruction.

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.”

But perhaps we have comforted ourselves by the idea that so long as the objectionable things we should not like others to hear remain as thoughts only, no great harm is done. But is not this argument a delusion? Scripture says “As he thinks in his heart, so is he.” (Prov. 23:7) And how often is the Lord's knowledge of men's thoughts recorded! Would He have answered them if they did not matter because they were never expressed? (Luke 2:35, Luke 5:22, Luke 6:8, Luke 9:47, Luke 11:17) The word of God, too, is “a discerner of the thoughts and intents of the heart.” (Heb. 4:12)

The entertaining of a foolish thought, to say nothing of the utterance of an idle word, proves that sinful flesh is still in us. To persuade ourselves into thinking otherwise would prove that we are deceiving ourselves as to the true nature of sin, regarding it only as the committing of outward acts of reprehensible or immoral nature. The holiness to which we are called goes far deeper than merely the avoiding of wrongful outward acts.