I work regularly with a good friend of mine to memorize Bible passages to encourage each other and hold each other accountable in our Christian walk. At present we are working on Matthew 5:27–30, a passage that hits me right between the eyes every time I read it. In it Jesus addresses the issue of lust by way of the prohibition against adultery:
You have heard that it was said, "Do not commit adultery." But I say to you that whoever looks at a woman to desire her has already committed adultery with her in his heart. If your right eye causes you to sin, tear it out and throw it away! It is better to lose one of your members than to have your whole body thrown into hell. If your right hand causes you to sin, cut it off and throw it away! It is better to lose one of your members than to have your whole body go into hell.
Jesus first cites the seventh commandment from Exodus 20:14 and Deuteronomy 5:18: “Do not commit adultery.” However, Jesus goes deeper than the physical act of adultery to the sinful condition of the heart which occasions it: lust towards another. His identification of the problem first deals with an action and its intent: “whoever looks at a woman to desire her.” It is clear that the problem lies not in the physical action of looking at a woman; instead it is in the motivation for doing so and the internal attitude which accompanies the visual sense perception. The verb ἐπιθυμέω (epithumeo) refers generically to strong desire or longing, but often it carries the specific nuance of sexual desire as it clearly does here; this phrase could be loosely paraphrased as “whoever looks at a woman with sexual interest” or “for sexual fulfillment.” This internal desire and purpose is condemned because of its logical end result: This person “has already committed adultery with her in his heart” and is as guilty as the one who participates in the physical act. Jesus’ description of the location of the act in the heart is apropos for the discussion at hand, as it shows that the problem is one of the inner person, and the solution must alter the inner person for it to be effective. The hyperbolic commands in vv. 29–30 illustrate the extreme desire for purity of heart which should mark those who seek to follow the teaching of the Lord in this matter.
This antithesis condemns not just the outward action of adultery but more importantly the state of the heart which occasions it. Jesus is most concerned not with what sort of sexual activity one engages but with the intent and desires of the heart. The ethics of the kingdom require that the heart be free of lust; the only proper path for the one who follows Jesus is to avoid the external action of adultery by first removing the internal compulsion of lust. Jesus here makes a claim on the inner person. The heart must be transformed so that the root cause of sinful behavior is removed.