Matthew 5:27–28

In the Old Testament, adultery — being unfaithful to your husband or wife to satisfy lust — had to be treated with great severity. Under the law of Sinai this sin had to be punished with death (Lev. 20:10; Deut. 22:22-24). First of all, the law gave God's rules for the outward and social life of His earthly people. That is why it punished only the completed act, even though the tenth commandment forbade coveting 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... But merely keeping this and all the other commandments on the outside could not justify him before God.

The prophets of old had come before the people with "Thus says the Lord" on their lips... but in the Sermon on the Mount Jesus stood up and said, "I SAY TO YOU." His teaching astonished those who heard Him, for He taught them as One having authority... He is able to look behind the profession and all that is outward, and read the heart, which none but God can do.

It is a scandalous and immoral procedure. He was shifting the searchlight from the outward actions to the unseen inner nature... the Lord went deeper. He dealt with the hidden desires of the heart, with the nature that lies at the root of every wrong act and from which all evil deeds spring. He declared that God required truth in the inward parts. In his great repentance David learned that his nature was more terrible than his deeds. The law taught Saul of Tarsus the same needed lesson (Romans 7). This did not make void the law; it established its use as a searching, convicting power.

The law was content to forbid the actual act; the Lord went further, and forbade not only the outward act but the inward desire.

Because of the teaching of the scribes and Pharisees, the Jews thought that simply keeping the law on the outside 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 some say. For the first time He reveals something that every honest Israelite had to learn by experience. Everyone who tried to keep the commandment "You shall not commit adultery" had inside them the very lusts that led to the actions God forbade. They had no strength to overcome them. The commandment even stirred those lusts up: "...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 Lord is not speaking here about accidental, unplanned looks that a person can barely avoid. He means the deliberate look of lust... So the sinful thought in the heart comes before the deliberate look.

Anything in our walk, our ways, or our service that puts a soul in danger of giving in to these impure desires should never be spared. We must leave it at any cost... Cutting off these parts of the body pictures a heart fully exercised in self-judgment. Such a heart does not excuse itself by saying that it never committed the sin. It gives up whatever exposed it to that sin.

Avoiding the act itself might satisfy a Pharisee or scribe. But the Lord could not do without truth in the inward parts... it is not the outside only that God regards, but the heart above all. Only a new nature delights in holiness. The person who has it by grace answers to the will of God his Father. He hates himself if he slips even into a wrong look, as something unworthy of his calling and hateful to Him who loves him.

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.

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).

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.

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."

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).

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.

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.