Matthew 5:
27 “You have heard that it was said, ‘You shall not commit adultery.’ 28 But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart. 29 If your right eye causes you to stumble, gouge it out and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell.
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It is not clear to me whether, in 5:27, Jesus is referring to women in general or only to married women. A straightforward reading would suggest that Jesus is saying that it is a sin to look at any woman lustfully.
Against this view would be that this would redefine what the word "adultery" usually means. But, on the other hand, that might be exactly what Jesus was trying to do, there.
To be safe, beil, I'd suggest that you avoid looking at any woman with lust. After all, you don't want to end up in hell for committing adultery in your heart, do you? The risk is too great.
If you're a heterosexual man, it might be difficult to avoid having the odd lustful thought about women who are passing by. So to be extra safe, you probably shouldn't ever go out of the house, and if you do be sure to wear a blindfold if there's any chance you might see a woman.