What does Matthew 5:28 mean?
Jesus has quoted the seventh of the Ten Commandments (Exodus 20:14), as taught to His listeners by the scribes and Pharisees (Matthew 5:27). This prohibits adultery. Now He begins to show that merely avoiding physical acts isn't good enough to satisfy the intent behind God's command. God wants His people to be pure in heart, as well as in their actions. This is part of a consistent pattern of Jesus' teaching, which is that attitudes and thoughts can be just as much sins as actions and speech.The connection Christ makes here is striking and would have been shocking to His original listeners. His claim is that lustful intent—all by itself—is a sin, an act of adultery in the heart. Legalists of that era might have claimed that lust and fantasy were fine, if it didn't lead to actual sex. But Jesus describes lustful intent as being every bit as much a sin as adulterous action.
The stakes of this comment are easy to miss, from a modern perspective. Adultery was an especially serious crime in that culture, punishable by death (Leviticus 20:10). Jesus is suggesting that a person's thoughts can be sinful on the same level as a capital offense. Some of Jesus' hearers may have received this statement in despair. How many can honestly claim to be entirely free of both anger (Matthew 5:21–22) and inappropriate desire? Jesus continues to raise the standards, making it sound harder and harder to get into the kingdom of heaven. Who could be so righteous?
In part, Jesus is pushing that very point: that nobody is righteous enough. All are sinful. At the same time, He is showing the expectation Christians ought to have for their inner, private lives. Christ is leaving no room for legalism or technicalities—He is defining sin as something which begins and continues in the heart.
Despite common misunderstanding, Jesus is not saying that all attraction is immediately sinful. The phrase used in Greek here is pros to epithymēsai autēn. This strongly implies something deliberate: an intentional, considered choice. "Noticing" that someone is attractive is not a sin; looking with sexual intent, fantasizing, or leering—what in English might be called "ogling"—certainly is. This phrase implies someone engaging their imagination in lust.
Some scholars suggest this phrase can also imply an additional possibility: looking at a woman in order to get her to lust. This would infer seduction: looking—or behaving—towards that person in a way that tempts them to inappropriate actions or thoughts. Whether that is the literal intent of Jesus' words here, the concept fits in the scheme of His overall point. The desire for adultery, even if it fails to succeed, is just as much a sin as accomplishing it. In either case, it's still about what is going on in the person's heart and not just the action.
Modern readers should also note that while Jesus phrases this—and other statements—using references to men and women, the spiritual principles apply to both sexes.