Adultery and lust (from the Sermon on the Mount) – even secret thoughts and minor actions constitute sin (Matthew 5:27 – 5:30)
Continuing his Sermon on the Mount, Jesus told his followers: “You have heard it said that you should not commit adultery. But I tell you that anyone who looks at a woman with lust has committed adultery with her in his heart. Therefore, if your right eye causes you to stumble, pluck it out and throw