27 You have heard that it was said,
'YOU SHALL NOT COMMIT ADULTERY';
28 but I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart.
29 If your right eye makes you stumble, tear it out and throw it from you; for it is better for you to lose one of the parts of your body, than for your whole body to be thrown into hell.
From the Sermon on the Mount