This is a pretty strong set of verses but definitely worth digging into. Matthew 5:27-28 says this:
“‘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.”
Bibleref.org explains it like this:
Now Jesus says that His listeners have heard, “You shall not commit adultery.” This is the seventh of the Ten Commandments (Exodus 20:14), taught to every Jewish person by their religious leaders. When Jesus uses the “you have heard” phrase, He does not mean to imply that the statement is false. Rather, He follows those statements with a more accurate understanding. Jesus does not go on to contradict the law against adultery—He magnifies it.
As he did before, Jesus will point out that it’s not “good enough” to simply avoid physical sin. What we think in our hearts leads to what we do with our bodies—so honoring this commandment means something more than not having sex outside of marriage. God’s intent is for people to control what happens in their hearts and minds well before the opportunity for physical adultery becomes available.
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.
So it all comes down to the heart. The heart is where it all begins and where it all happens. His teaching here is a teaching for us to keep our hearts and our minds….clean. Again, our entrance into the kingdom of Heaven is impossible without the intervention of Christ.
Christ in our minds. Christ in our hearts.
It’s so hard to do this on our own. We need Jesus in it all. We need Jesus in every aspect of our lives, our minds, our hearts.