I am dismayed to see that NASB has changed their translation of Matthew 5:28. I’m pretty sure it used to say that everyone who looks at a woman to lust for her has already committed adultery with her in his heart. It now says “everyone who looks at a woman with lust for her”. That’s very different. The second makes it sound as though if we look at a woman and lust spontaneously arises, that is adultery in the heart. The first implies that it is looking at a woman in order to lust – for the purpose of lust – that is adulterous. That is the real meaning, in my opinion. I like ESV’s translation: “everyone who looks at a woman with lustful intent has already committed adultery with her in his heart”.
I have three reasons for thinking the intent-based meaning is the correct one. First, the Greek preposition is closer to “to” than to “with” (I think?). Second, the phrase “has already committed adultery in his heart” points to the sin having happened before he looked. Third, this interpretation makes sense of the distinction between temptation and sin, without surrendering the important idea that attitudes and intentions can be sinful even without our acting on them.