Adultery is a crime of selfishness and lust.  It involves a betrayal of fidelity. According to the Old Testament adultery was punishable by death, but in his sermon Jesus gives us a deeper understanding of adultery.  Jesus contradicts the common idea that the act of adultery takes place at the moment of intercourse.  According to Jesus the sin begins with selfishness and lust within the heart of men that finally consummates in intercourse. 

It begins with the lust of the eye when it looks upon a woman with desire.  At this point the fidelity of marriage is already broken.  This is the spiritual sin that takes place prior to the physical one. Many cannot believe that Jesus really means what he says here.  The claim is that no one can go through life without lusting after another person—at least not in our society where advertising is based upon the very idea of lust.

Jesus makes it very clear that this is not some exaggeration that is supposed to somehow scare us into holiness or is aimed only at monks, priest, and saints.  In the very next verse he tells us that if our eye or hand offends us we must cut it off and throw it away for it is better to enter heaven with one eye or one hand then enter hell with two.

This is not an exaggeration.  It is an example of how serious we must take the commission of sin.   When war vets enter into war against our enemies they know that they might lose an eye, a hand, leg, or even their lives. They are given metals for bravery when such things happen and looked up to by society as heroes.  But when Jesus asks this same dedication of us towards our enemy of sin we turn away and want to believe that he is exaggerating.  Why would we be willing to offer more for our country than for our Lord and God?

So the main point to take away from this commandment is the seriousness and pervasiveness of sin in the human heart.  This is where evil begins. The only remedy for such a sin is faith as we shall see later.