Editor’s note: The purpose of this series is to walk our readers through the Sermon on the Mount in Matthew 5-7 in order to help them understand what it teaches and how to apply it to our lives. This is our first such series here at Servants of Grace through an extended biblical passage and is part of our larger commitment to help Christians learn to read, interpret, reflect, and apply the Bible to their own lives.

SermonOnTheMountThe Heart of the Matter

In the previous passage, Matthew 5:21–26, Jesus told His disciples that they not only must not murder, but must not harbor the anger and contempt that lead to murder. Instead, we should be reconciled to our brothers and sisters when something stands between us. Indeed, we should even strive to make peace with our enemies.

Jesus pushed beyond external deeds to probe the motives that lead to murder. Now He does the same thing with adultery. He briefly addresses our physical deeds, but He chiefly explores the heart issues behind adultery.

While Jesus probes the heart of the matter, our public discourse becomes ever more superficial. Our comedies treat adultery and fornication as jokes. Our commercials and clothing styles promote lust. Our public policies assume that everyone over the age of eighteen is sexually active. And we deride the concept of absolute standards. But then we fret over the consequences of sexual immorality, such as teenage pregnancy and the host of sexually transmitted diseases, starting with AIDS. The solution, society proposes, is not fidelity within marriage and abstinence outside of marriage, but “safe sex” and condom distribution.

The Moral Standard

Jesus begins by restating the seventh commandment, “Do not commit adultery.” Perhaps everyone agrees that murder is wrong (Matt. 5:21), and perhaps a solid majority still affirms that adultery is immoral. But the gap grows wider in practice. A large church probably has no murderers in attendance, but it probably has many who have either committed adultery or suffered from it.

If someone has committed a sexual sin, God offers forgiveness if he or she repents. Whatever the sin may be, Scripture says, “If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness” (1 John 1:9). Once someone is forgiven, he or she seeks each day to be faithful and obedient. Further, if God is willing to forgive all those who are genuinely repent, then those who suffer adultery should also forgive them, forgo vengeful anger, and, if possible, trust their spouse again.

Adultery is Jesus’ principal concern, for two reasons. First, it is the most grievous sexual sin, for it betrays the promise of lifelong, exclusive loyalty. Second, almost all Jews were married before the age of twenty, so that the leading sexual temptation was adultery, not fornication. But today, in nations where people reach sexual maturity earlier than ever and the time of marriage is often later than ever, the leading temptation is fornication.

Yet whether adultery or fornication is the greater issue, Jesus presses deeper. Just as Jesus forbids the anger that leads to murder, so also he forbids the lust that leads to adultery. He cares about more than physical acts and superficial definitions of purity, but about the heart, and the motives. Therefore he says, “Anyone who looks at a woman lustfully has already committed adultery with her in his heart” (Matt. 5:28 NIV). The ESV translates this verse as “Everyone who looks at a woman with lustful intent has already committed adultery with her in his heart.” The ESV hints at a small riddle in the text. The original Greek may be translated “Anyone who looks at a woman in order to lust after her” (cf. KJV, NASB) commits adultery. That is, Jesus forbids the leering looks that are intended to stir up lustful thoughts. But the Greek may also be translated, “anyone who looks at a woman so as to cause her to lust” commits adultery. In this case, Jesus opposes the man who looks at a woman and wonders how he can cause her to desire him, so he may seduce her.

Jesus warns men against such sins, but surely women should neither lust nor attempt to stir up lust in others, either. Wise women know that it is one thing to make themselves attractive and another to make themselves look seductive.

Beyond this, Jesus forbids all sexual acts outside of marriage, not just adultery per se (Matt. 15:19; 19:9). Premarital sex is not compounded by the betrayal of a promise of lifelong, exclusive loyalty. But it is still sin before God, against others, and against oneself.

Homosexual unions also constitute an intimate relationship outside the bounds of marriage, so they also violate God’s will. Sexual expression belongs inside the love, the commitment, and the safety of marriage between one man and one woman for life. We should have compassion for those who struggle with same-sex attraction, but we cannot bless homosexual unions without doing violence to Scripture (Gen. 19:4–11; Lev. 18:22; 20:13; Judg. 19:22–25; Rom. 1:24–27; 1 Cor. 6:9; 1 Tim. 1:10).

Is Jesus Too Strict? Reasons for His Standards

Lust is the problem Jesus addresses in Matthew 5:28, but before we consider that, we should address those who question the idea that physical intimacy belongs only in marriage. In high schools and colleges, and among single adults, many question this biblical teaching. The argument goes like this:

The laws against adultery may have been necessary long ago, for social reasons: to prevent birth outside of marriage. They also protected women, who were so dependent on men. But now we can solve the problem of unwanted pregnancy. And today’s women, so liberated, so educated, need not depend on men any longer. So the rationale for prohibiting these acts is outdated. People should be free to choose their own lifestyle.

Instead of answering this directly, let us consider the way too many Christians respond to such challenges. Lewis Smedes, a Christian ethicist, says that Christians defend the biblical teaching in three somewhat inadequate ways. He calls them the morality of caution, the morality of concern, and the morality of personal relationship.

The morality of caution asks, “Can I get hurt?” and answers, “Yes.” According to this approach, we should avoid extramarital sex because it is dangerous and painful. It leads to serious and even deadly diseases. It causes guilt and unwanted pregnancies, emotional pain, and self-corruption. These points are generally valid, but they operate on the basis of a cost-benefit analysis, and a cost-benefit analysis cannot support an absolute veto on extramarital sex. After all, people persuade themselves that the cost is worth it, or that they can control the consequences.

The morality of concern asks, “Can I hurt others? What if I cause a pregnancy or a disease? What if I bring guilt or sorrow to another?” This reasoning seems less selfish than the first. But again, it rests on a cost-benefit analysis, and passions can lead people to think that the benefits are clear and the costs are controllable.

The morality of personal relationship asks, “Can this hurt our relationship? Will one of us exploit the other sexually? Will the move toward sexual gratification hurt other aspects of our relationship? Will the tender, gradual process of self-disclosure be cut short by the quick charge of sexual gratification?” As Smedes says, in sexual intimacy, there is “such explosive self-giving, such personal exposure, that few people can feel the same toward each other afterward.” One partner may yearn for a commitment that the other is unwilling to make. Then one feels needy and the other feels trapped and looks to escape.

The “morality of personal relationship” still has a whiff of self-interest and cost-benefit analysis, but it takes us closer to the divine plan that places sexual expression inside marriage. In God’s design, three things go together. As God told Adam and Eve, “A man will leave his father and mother and be united to his wife, and they will become one flesh” (Genesis 2:24). Then we read, “The man and his wife were both naked, and they felt no shame” (Genesis 2:25). This is the God-given trio:

  1. Exclusive loyalty. Father, mother, and the dearest friends take second place.
  2. Lifelong loyalty. Husband and wife are united to one another.
  3. Bodily loyalty. Husband and wife become one flesh. They express and seal the union of their hearts and minds with the union of their bodies.

By its very nature, physical love is a life-uniting act. God intended it to be a sign and a seal of the union of two lives. “Casual sex” is a misnomer. Sex is no mere bodily function. Our bodies are us. To quote Smedes again, “When two bodies are united, two persons are united. Nobody can go to bed with someone and leave his soul parked outside. The soul is in the act.”

Therefore, the trouble with extramarital sex is that it is “a life-uniting act committed without life-uniting intent.” It is not just adultery. It is a thieving lie. Intimacy is a sign and a seal of the union of two lives. But outside of marriage, the act and the intent clash. Intimacy of body and intimacy of soul go together. That is why adultery—as well as other sexual relations outside of marriage—is wrong.

Lust: The Mind for Adultery

After Jesus forbids adultery, He warns against lustful eyes, against adultery in the heart. Jesus cautions men about lustful eyes, for men are more oriented to seeing than feeling. But our culture is trying hard to teach women to lust after “eye candy” too, so Jesus’ warning applies to them as well.

We must understand what Jesus forbids. It is harmless and natural to notice that a woman is beautiful or that a man is handsome. But it is one thing to make an aesthetic observation, another to turn it over to the imagination and entertain immoral fantasies. Likewise, it is good to dress attractively, but not to dress seductively.

The fashion industry is not necessarily the friend of chastity. In 2002, social critic David Brooks observed that “the average square yardage of boys’ fashions grows and grows while the square inches in the girls’ outfits shrink and shrink, so that while the boys look like tent-wearing skateboarders, the girls look like preppy prostitutes.” That is today’s problem. In five years, the problem will change, but the essence remains the same. The clothing industry rarely promotes modesty.

Jesus says adultery begins in both the heart and the eye. The heart moves the eye, and the eye inflames the sinful heart. Adultery doesn’t just happen. Adultery with the body follows adultery with the heart and the eye. Knowing this, righteous Job said, “I made a covenant with my eyes not to look lustfully at a girl.… If my heart has been led by my eyes … [or] my heart has been enticed by a woman,” may the Lord punish me (Job 31:1, 7, 9).

We understand that it is not sinful to be tempted. Temptations assail us all—even Jesus was tempted. Jesus was “tempted in every way, just as we are—yet was without sin” (Heb. 4:15). So then, Jesus faced the temptation to entertain lustful thoughts, but He resisted. He refused to envision or plan or taste sin, even with His mind.

We cannot prevent certain thoughts from entering our minds. But once they enter, we may either entertain them or cast them aside and turn our minds elsewhere. Martin Luther said that we cannot stop birds from flying over our heads, but we can keep them from building nests in our hair. We cannot keep impure thoughts from flitting into our minds, but we can refuse to let them roost and find a home there.

The Goodness of Sexuality and Imagination

While we affirm that Jesus wants His disciples to resist certain sexual thoughts, we must remember that sexuality is good. Like all of God’s creations, sexuality is good in itself. Since sexuality is part of human nature, sexual desire is proper and natural. Yet, like all good things, it must be used the right way, in the right place and time. Similarly, food is good, but there are times when it is wrong to eat. Sleep is good, but there are times when it would be immoral to take a nap (a physician, during surgery, for example). So too, sex is good in the right place and time and wrong in others. The right place is the commitment and safety of marriage between one man and one woman. God blesses sexuality when it is surrounded by loving faithfulness between a man and a woman (Prov. 5:15–19).

God wants to bless our use of His gifts, as we use them the right way. A vivid imagination is also a gift from God. Almost all of the world’s literature depends upon it. For us to witness the torment of Hamlet or the courage of Henry V, Shakespeare had to imagine it first. Great leaders must first imagine a better future. Inventors must imagine better ways to live and conceive of means to achieve them. God blesses such uses of the imagination. But if we turn the imagination toward taking what does not belong to us, it corrupts the mind and can lead to actual misdeeds. Therefore, Jesus warns against lust.

Recoiling from Lust

Lust is a form of coveting, and coveting is the gateway to many sins, including adultery. Jesus shows how serious lust is when he says, “If your right eye causes you to sin, gouge it out and throw it away” (Matthew 5:29). This is hyperbole, of course. In all of church history, no group of Christian leaders ever endorsed literal mutilations or amputations. Indeed, the Council of Nicaea formally forbade it. Besides, if Jesus thought mutilations and amputations could actually cure evil, He would have ordered His disciples to put out both eyes, for a one-eyed man can still lust, and to cut off both hands, for a one-armed man can do terrible evil. Indeed, even the removal of both eyes would not suffice, for the memory can still “see.” The root of sin lies in the heart, not in sense organs or limbs.

The point, then, is that it is better to suffer bodily pain in the present than to suffer spiritual pain for eternity. So we can be sure that Jesus does not want us to take this sentence literally. Still, we have to decipher Jesus’ figure of speech.

First, Jesus used repugnant, grotesque images to show how repugnant and grotesque sin is in His sight. Few things are more horrible than the thought of maiming. Yet Jesus says, “It is better for you to lose one part of your body than for your whole body to be thrown into hell. And if your right hand causes you to sin, cut it off and throw it away” (Matthew :29–30). If Jesus says it is better to go through life maimed than to enter hell whole, then sin should seem horrible to us. We should shudder at the thought of it, as we shudder at the thought of losing a limb.

Second, if our eye tempts us to sin, we should strive to act as if we had no eye, and refuse to look at the tempting object. If a hand or foot tempts us to sin, we should act as if we had none, by refusing to walk toward that which tempts us and by refusing to touch the source of temptation.

This teaching applies to pornography, which is so accessible today. Pornography is wrong in many ways. It degrades women and teaches them to degrade themselves. It inflames lust. It is unfair to spouses, present or future, who cannot compete with models who polish their bodies for a living while photographers delete all defects.

When we come across pornography, we should strive to live as if we have no eyes. Yet we do have eyes, and pornography gains a strange grip on some people, almost like an addiction. Let me suggest three things to those who may be tempted by it:

  • Keep yourself away from temptation. Avoid the books, movies, websites, and magazines that lead you into temptation.
  • If self-control is difficult, if the sin is getting a hold on you, tell someone and give him (if you are a guy) or if you are a lady, another lady, the right to ask you about your progress against this sin.
  • If such a sin gains a grip on you, seek a Christian counselor..

In our verses, Jesus connects sexual sins with Gehenna, the place of punishment. That does not mean that everyone who commits sexual sins goes to hell. By God’s grace, every sin is forgivable. But if we love the thought of sin, and indulge it instead of resisting it, we are rejecting God’s ways. Deliberate rebellion does lead to death. But if we take our struggles to the Lord, seeking mercy, He will forgive us and renew us.

Contentment: The Antidote to Lust

Contentment is the antithesis of lust. The Bible often commands believers to be contented with their possessions and with their life situation (e.g., Eccl. 4:8; Luke 3:14; Phil. 4:11–12; 1 Tim. 6:6–8; Heb. 13:5). Paul says, “Godliness with contentment is great gain” (1 Tim. 6:6)—not material gain, but spiritual gain. The general command to be content means we should be content with our singleness, if that is God’s gift. If we are married, it means that we should be content with the spouse that God has given us.

Our culture encourages us to be discontented with many things, including our spouses. It presents images of fitness and beauty that few people can match. Movies imply that singles who lack a partner are missing the best thing in life. Television comedies show us how entertaining it is to mock and ridicule a spouse who lacks a scintillating wit and endless talents. Some self-improvement gurus tell us that we are right to be discontent if our spouse simply isn’t keeping up with us.

Of course, every husband or wife has failings. We fail to listen, leave messes, and hog the covers. It is no sin to notice these flaws, but it is a sin to become discontent with the spouse that God has given us. Discontentment with a spouse drives out love and respect for her. Discontentment is prideful, for the discontented think they deserve better. Discontent is distrust in God’s providence, for it accuses God of providing the wrong spouse. The culture says, “Get the best partner you can.” But we should say, “God has given me this man, this woman.” Then we should ask not what our spouse can do for us, but what we can do for our spouse. Contentment is the partner of love and the scourge of the roving eye. Contentment breeds faithfulness.

The Heart Issue

Wherever they begin, marital problems end with the heart. Success in marriage depends on our response to events more than it does on the events themselves. The cause of lust is not attractive women, but an improper response to attractive women. The cause of marital discontentment is less “my spouse’s flaws” than it is a hard-hearted response to those flaws.

There is no ideal man or woman. Every one of us is flawed from head to heart to hands. The unmarried seek a compatible partner, but in an important way the quest is vain. Every potential partner is a sinner, and no two sinners are perfectly compatible. No two sinners, rubbing elbows day by day, can keep their wedding vows perfectly.

People love to ask questions like “What are the two biggest causes of trouble in marriage?” There are many potential answers: money, sex, children, in-laws, communication. But the two biggest causes of marital strife are the husband and the wife. The solution to all of these problems is the gospel of Jesus Christ. Jesus desires to bring freedom to captives to pornography, adultery, and lust. He did this by dying in the place of sinners for their sin so their hearts of stone could be replaced with a new heart, and they could be given new desires and new affections for Himself. If today your struggling with an addiction to pornography I encourage you to seek out one of the pastors at your local church. In the meantime, I urge you to repent, confess your sin, and turn from it by turning to Jesus Christ the One who loves you so much He died in your place for your sin so you could put all of your sin to death and live for Him by His power through the work of the Holy Spirit.