But *I* say unto you, that every one who looks upon a woman to lust after her has already committed adultery with her in his heart.
Jesus takes the command against adultery and pushes it past the act to the look, and past the look to the desire behind it. The question He raises is not "have I kept the rule?" but "what is in my heart when God looks at it?"
Upholding the law, not setting it aside
Because Jesus adds to what the law said, some conclude He was replacing it. One writer answers that objection using this very verse.
Take one example out of the seven times in that discourse when our Lord said, "I say to you." "You have heard that it was said, 'You shall not commit adultery.' But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart" (Matt. 5:27-28). Where is the setting aside of the law? No — He upheld it. The law was content to forbid the actual act; the Lord went further, and forbade not only the outward act but the inward desire.
Why the heart had to be exposed
The scribes and Pharisees — Israel's religious teachers — measured obedience by outward conduct. Against that background, the Lord's words did something no one had heard before.
Because of the teaching of the scribes and Pharisees, the Jews thought the mere outward keeping 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. He reveals for the first time something every honest Israelite had to learn by experience. Everyone who tried to keep the commandment "You shall not commit adultery" already had inside them the very lusts that led to the acts God forbade. And they had no strength to overcome them. The lusts were even stirred up by the commandment: "for I would not have known what it is to covet if the law had not said, 'You shall not covet'" (Rom. 7:7-11).
The deliberate look, not the accidental one
The verse describes a look with intent, and that distinction decides how the words apply day by day.
This distinction is very important. Today we can hardly go anywhere without seeing the moral corruption of our time. We do not mean to see it, and it defiles us easily. The intentional covetous and sinful look is something completely different. No Christian can stop unclean thoughts rising in his mind. They become sin only when he turns toward them and gives himself to them instead of turning away. Covetous looks and unclean thoughts are sin. So it is also sin when believing women and girls stir them up by their dress and behaviour.
The same writer knows the opposite danger — a conscience so tender it condemns itself for what it never chose.
God-fearing Job said: "I have made a covenant with my eyes; how then could I gaze at a virgin?" (Job 31:1). But some Christians are over-sensitive and over-anxious. Involuntary looks and thoughts weigh their consciences down. I would remind them of the well-known words Martin Luther wrote on this verse: "I cannot stop a bird flying over my head, but I can stop it building a nest in my hair or biting off my nose."
Willpower cannot reach the desire
Advice to simply try harder fails at the exact point this verse targets.
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 resolve and perseverance. But this advice overlooks one thing. Willpower alone may check the wicked deed, but the sinful desire has already filled the heart. And divine holiness uncovers the secret source of inward evil. In God's sight, a foolish thought is sin. Our Lord condemns the lustful look and the adulterous act alike (Matt. 5:28).
What does work is a changed nature, and it shows itself in how a person reacts to even a single wrong glance.
The avoidance of the extreme act might satisfy a Pharisee or a scribe; but the Lord had to have truth deep inside a person. Only a new nature delights in holiness. The one who has it by grace answers to the will of God his Father. If he slips even into a wrong look, he hates himself for it, as unworthy of his calling and hateful to Him who loves him.
The response the Lord asks for
The verses that follow name the eye and the hand, and commentators read them as a call to cut off whatever leads that way.
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 abandoned at any cost… The cutting off of these members pictures a heart thoroughly exercised in self-judgment; not excusing itself by saying that it had not actually committed the sin, but giving up whatever exposed it to that sin.
Summary
- Source. Adultery does not begin in the act; the Lord points to the heart and shows that the sin has its source there.
- Standard. The law forbade the act, and He forbids the desire behind it — not setting the law aside but carrying it inward.
- Sin. Unavoidable sights are not the issue. A thought becomes sin when you turn toward it instead of away.
- Strength. Willpower can check a deed, but not the desire that filled the heart first. Only a new nature delights in holiness.
- Surgery. The right response is unsparing self-judgment — refusing the excuse "I never actually did it," and giving up whatever exposes you to it.