Jesus’ Sermon on the Mount: Lust; Confronting Sexual Sin in the Mind

“You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart. If your right eye causes you to sin, tear it out and throw it away. For it is better that you lose one of your members than that your whole body be thrown into hell. And if your right hand causes you to sin, cut it off and throw it away. For it is better that you lose one of your members than that your whole body go into hell” (Matthew 5:27-30).

Let’s consider the first two verses there.  Jesus points out that the Law of Moses says “you shall not commit adultery.”  That’s clear and straightforward.  However, we need understand that adultery doesn’t simply spring out of nowhere and ambush a poor, innocent, unsuspecting soul.  Jesus again points to the fact that the sin of adultery has a source, and that source is the human heart.  And within the heart, there we can find the root of adultery, which is lust, the desire for that which is off limits to you. 

In the same way that anger, stored up in the heart is sin, so also lust, if it’s not resisted, is sin.  Now, this doesn’t mean that noticing that someone is attractive is a sin.  If that were the case, I think we’d all be up the creek.  The issue here is when that notice then becomes a lingering look, which then becomes an image in the mind, which then becomes fantasy.  Do you see?  Here’s that same slippery slope language that we saw when Jesus spoke about murder.  Sin begins with a seed that takes root in our hearts and then escalates until it shows out, and bears fruit.  So it is with adultery, and I’m going to include fornication here also, because fornication is explicitly mentioned in other places.  Adultery is unlawful sex with someone other than your own husband or wife, and fornication is unlawful sex outside of marriage.  The only sex that pleases God, and there is such a thing because God created sex, is sex between a man and a woman in the covenant of marriage.  All other sexual activity is out of bounds, that is, beyond the boundaries that God created for it. 

Think about fire.  Fire in one sense is very good and useful.  It keeps us warm in winter.  We can cook with it.  It’s nice to look at.  But that’s fire within very defined boundaries.  If fire gets outside those boundaries, it becomes destructive.  Fire in the fireplace is a good thing.  Fire on the living room floor, bad thing!  It’s the same with sex.  God created sex with clearly defined boundaries for all the right reasons.  Sex within these boundaries is awesome, but the second it breaks outside those boundaries, it burns the house down. 

Jesus deepens the Law and internalizes it here.  Lustful intent is the same as adultery.  The second look, the lingering gaze, the fantasy that develops in your mind, that’s where your battle is.  That’s where the child of God must fight the good fight.  And that fight must be violent.  Jesus tells us as much.  Look at V.29, “If your right eye causes you to sin, tear it out and throw it away!”  That’s brutal!  That’s shocking.  Jesus intends for it to be.  We must be violent with these sinful urges.  Why?  -Because if you lose the battle in your mind, you’ve already lost.  And because eternal life is what’s at stake.  It’s much better for you that you get rip-roaring aggressive with what’s leading you to have lustful thoughts than for you to self-destruct.  Does Jesus really mean for you to rip your eyeball out?  No.  This is hyperbole.  This is a rhetorical device Jesus uses often, so that he can get his point across.  But the things you might need to do take your sin seriously might look as crazy to some. 

Let me give you an example.  I discovered just after I became a Christian, in that season of my life how difficult it was to resist this slippery slope when I would notice someone who was attractive.  But here’s a verse that I adopted as my fighting verse whenever I’d run into temptation.  Job said, “I have made a covenant with my eyes not to look lustfully at a woman” (Job 31:1).  And here’s a thought technique I would use to resist invasive, lustful thoughts; I would bring an image into my mind of doing physical harm to Satan or to demons, because I recognized that these were my enemy.  I’d imagine an ax or a hammer or even a baseball bat that I’d use to beat back the enemy.  And, while I don’t know what would work for you, that worked for me, it was my own way of resisting temptation, of taking every thought captive so that I could obey Christ. 

You might be one of those that say, “Now, that just sounds crazy.  You sound like a crazy person.”  And to that I’d say, “It’s better to tear out my eye than for my whole being to be thrown into hell.  It’s better that I lose my right hand, than to be destroyed.”  For some of you, it might be better that you lose your laptop or smartphone so that you aren’t tempted anymore to look at pornography.  “Well, that sounds extreme!”  Yes- that’s exactly Jesus’ point.  That’s how serious sin is.  And sexual sin is especially intense and dangerous, which is why we have to take extreme measures against it. 

So, let’s try to sum up what we’ve learned and put it into the overall context of the Sermon on the Mount.  Then I want to try to draw out some other related applications.  Remember that the sermon on the mount is all about how citizens of God’s kingdom should live in a broken world.  To live as a child of God in this world, especially in this current cultural situation, where morals are very loose, we must confront sexual sin.  We must call sin by its name. 

-The Bible calls out any sexual activity outside of covenant marriage between a man and woman as sin that leads to hell.  To deepen and broaden this, sexual sin begins in the heart with lustful intent.  *An unrestrained mind when it comes to sexual sin is as bad as adultery.

- Jesus’ remedy for confronting sexual impurity is to get violent and in the wise words of the philosopher, Barney Fife, “Nip it in the bud,” before it burns you down.

Now, before we finish, I just want to draw some other conclusions from what we’ve learned.  Viewing pornography, whether you are a man or a woman, is adultery.  You can’t view that stuff without fantasizing and that is infidelity.  Your sex is for your spouse only; in the words of Proverbs 5:15, “Drink water from your own cistern, running waters from your own well.  Should your springs overflow in the streets?”  Let’s get serious about pornography.  I need to mention a growing trend of, so called, Christian young people living together before marriage (that is, living together in a sexual relationship before marriage).  Many of these argue that because they intend to get married, there’s no harm in it.  But the problem with that is, outside of marriage they haven’t made any legal commitment to this other person yet.  There are no bonds yet to be broken, they could just as easily brake up, because there’s no costly divorce to deal with.  Marriage comes with strong legal and social obligations.  If you aren’t ready to make those obligations, wait!  If you are, get married already.  Paul says, “Don’t just be burning with desire.”  Get married.  Living together before marriage (being sexually active) is fornication, which is a sin because it’s outside God’s boundaries for sex.  -Another thing we need to mention.  There’s a big, big cultural push, lots of cultural pressure nowadays, to accept and to celebrate homosexuality as morally right.  But the clear, consistent teaching on this from the Bible is that sexual activity between members of the same sex is sin, outside the bounds that God has created for sexual activity.  We have to hold to the clear teaching of Scripture even when it is counter cultural.  Last thing, modesty.  I realize this is a little hot-button, and it’s very bound up with cultural norms, but I think we have a pretty good understanding of what kinds of clothing would lead to sexual provocation.  So, we all need to be careful that we’re not putting a stumbling block in any brother or sister’s way.