Read Matthew 5:27-30
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 has already committed adultery with her in his heart. 29 If your right eye causes you to sin, tear it out and throw it away; it is better for you to lose one of your members than for your whole body to be thrown into hell. 30 And if your right hand causes you to sin, cut it off and throw it away; it is better for you to lose one of your members than for your whole body to go into hell. (NRSV)
Back in the very early days of the church, leaders had to warn sensitive men that they were not to take this teaching of Jesus literally. It seems quite a few men were walking around with one eye plucked out and one hand cut off. Jesus was rather making the point that to avoid dangerous lust you might need to take radical action.
Even so, the issue remains as to just what constitutes lust. Some people feel terribly guilty if they find someone of the opposite sex attractive. But admiring someone’s attractiveness is not the same as lust. Lust is actively thinking about doing something about it. Lust is not the first look but the second and third look.
This text is part of Jesus’ warning against seeing human sin as merely an outward act. A person might refrain from having sexual relationships with someone other than their spouse but inwardly they may be madly lusting after others. Jesus warns against patting ourselves on the back for not having extramarital affairs while all the time indulging in such affairs in our own imaginations.
The two best antidotes to extramarital misconduct are firstly to focus on what is good and honourable about those of the opposite sex, treating them with dignity in our minds as well as our acts. And secondly, to have a healthy marriage. Not much good warning our spouses against lust if our marriages are dry and withered.