Jesus' warning against lust would have challenged some ancient hearers' values. Many men in the ancient Mediterranean thought lust healthy and normal (for example, Ach. Tat. 1.4-6; Apul. Metam. 2.8); some magical spells even describe self-stimulation as a way to secure intercourse with the object of one's desire (PGM 36.291-94), even if she was married (PDM 61.197-216). Jewish writers, however, viewed lust far more harshly (for example, Sirach 9:8; 41:21; 1QS 1.6-7; CD 2.16); some, in fact, viewed it as visual fornication or adultery (see Keener 1991a:16-17). Yet Jesus is not challenging his hearers' ethics; the scribes and Pharisees may have agreed with his basic premise, but Jesus challenges their hearts, not just their doctrine. Many Christians today similarly profess to agree with Jesus' doctrine here but do not obey it.
Jesus offers an implicit argument from Scripture, not just a cultural critique. The seventh of the Ten Commandments declares, "You shall not commit adultery" (Ex 20:14), while the tenth commandment declares, "You shall not covet [that is, desire] . . . anything that belongs to your neighbor" (Ex 20:17). In the popular Greek version of Jesus' day the tenth commandment began, "You shall not covet your neighbor's wife," and used the same word for "covet" that Jesus uses here for "lust." In other words, Jesus reads the humanly unenforceable tenth commandment as if it matters as much as the other, more humanly enforceable commandments. If you do not break the letter of the other commandments, but you want to do so in your heart, you are guilty. God judges a sinful heart, and hearts that desire what belongs to others are guilty.
Jesus does, however, go beyond his contemporaries' customary views on lust. Jewish men expected married Jewish women to wear head coverings to prevent lust. Jewish writers often warned of women as dangerous because they could invite lust (as in Sirach 25:21; Ps. Sol. 16:7-8), but Jesus placed the responsibility for lust on the person doing the lusting (Mt 5:28; Witherington 1984:28). Lust and anger are sins of the heart, and rapists who protest in earthly courts, "She asked for it!" have no defense before God's court. Jesus says that it is better to suffer corporal punishment in the present-amputating one's lustful eye or other offending appendages-than to spend eternity in hell after the resurrection of the damned (5:29-30; 18:8-9).
Of course gouging out one's eye cannot stop lust; people can lust with their eyes closed. (Thus Tertullian warns that Christians need not blind themselves as Democritus did, but must simply guard their minds; he contends that "the Christian is born masculine for his wife and for no other woman"-Apol. 46.11-12.) Jesus is declaring in a graphic manner that by whatever means necessary, one should cast off this sin (compare Col 3:5). One must repent to be ready for the kingdom of heaven (Mt 4:17).
Herod Antipas, driven by lust, ended up murdering a prophet (14:6, 10; compare 5:11-12), illustrating the principle of both this paragraph and the preceding one (5:21-30), as well as the prohibition of oaths (5:33-37; 14:7). Most of us lack Herod's power to indulge our desires, but God knows what our hearts desire, whether we have power to execute that desire or not. How different the model of Joseph and Mary (1:25) and virtuous single persons like John the Baptist and Jesus, who suffered persecution for righteousness!
From this warning we learn the value that God places on marital and premarital fidelity. Even our thoughts should be only for our spouse; our spouse, rather than a given culture's idealization, should redefine our standard of beauty (compare Song 1:15-16). Of course, since the Bible demands faithfulness in advance to our future spouse (Deut 22:13-21; see also Mt 1:19), the principle Jesus illustrates with "adultery of the heart" could apply to premarital "fornication of the heart" just as well.
Jesus does not, of course, refer here to passing attraction. The Greek tense probably suggests "the deliberate harboring of desire for an illicit relationship" (France 1985:121). In our culture, where young people generally have to arrange their marriages without their parents' help, we might be in trouble if Jesus meant mere attraction! Jesus refers not to noticing a person's beauty but to imbibing it, meditating on it, seeking to possess it.
Lust is antithetical to true love: it dehumanizes another person into an object of passion, leading us to act as if the other were a visual or emotional prostitute for our use. Fueled by selfish passion, adultery violates the sanctity of another person's being and relationships; love, by contrast, seeks what is best for a person, including strengthening their marriage. Adultery usually involves considerable rationalization, justifying one's behavior as necessary or loving; but lust is the mother of adultery, the demonic force that allows human beings to justify exploiting one another sexually, at the same time betraying the most intimate of commitments where trust ought to abide secure even if it can flourish nowhere else. Lust demands possession; love values, respects and seeks to serve other persons with what is genuinely good for them. Lust is always incompatible with acknowledging God as the supreme desire of our hearts, because it is contrary to his will.
Legalism cannot change the heart and destroy lust or any other sin; only transformation of the heart to view reality in a new way can. Matthew frames Jesus' commandments in this section with that warning (compare 5:20, 48). Whereas lust distorts relationships, proper relationships in Christ's family can meet the need that lust pretends to fill. Paul and his contemporaries prescribed marriage as a helpful solution (1 Cor 7:2, 5, 9; Keener 1991a:72-74, 79-82), but many godly people today do not find marriage partners for years-and not all have the gift to easily embrace that state (Mt 19:11). How can they best guard against lust?
Once we begin to appreciate our brothers and sisters in Christ as members of our spiritual family, we are less apt to dehumanize them as temptations-whether temptations to be avoided or indulged. Our video culture has cheated us by reducing the meaning of gender to sexual gratification, as if we could relate to members of the other gender best as sleeping partners. God ideally gave people families in part so we could learn how to relate to other people in a variety of ways (motherly, fatherly, brotherly, sisterly-1 Tim 5:1-2); our Christian family is no different (1 Tim 5:1-2; see also Mt 12:49; 23:8; 25:40).
Thus giving and receiving genuine Christian love within the appropriate boundaries-dealing with people as human beings like ourselves rather than objects of our passion (22:39)-is an important defense against lust. Perhaps an even greater defense remains being so wrapped up in Jesus' presence and work that one can wait either for God to send a spouse or for the ultimate unity that transcends the need for marriage altogether (see 22:30). In the meantime, one can pray for God's blessings on and prepare one's own life for the person God may send, or pour one's whole commitment into the work of the kingdom (6:33). I suggest these insights not as a married man paternalistically advising singles, but as one who remains single at the time of writing. The longer we resist a particular temptation, the less power that temptation can exercise in our lives.