It Starts in Your Heart
Today I get to preach on another very well-known passage in the Sermon on the Mount. I’m assuming, as we begin this morning, that many of us are familiar with these words. Maybe you had the experience I had as teenager in youth group, when it felt like we would hear messages on this passage every three weeks or so.
These are words which smite our consciences and, I am sure, have already made some of us uncomfortable even as we’ve just read them together.
And it would be really to do what many of my youth leaders did: rush in, assume we know what these words mean, and jump immediately into applying them to our life experiences.
But we’re not going to do that. These words don’t stand on their own; they are part of a bigger context. And what they actually say may be less obvious than we think. So we’re going to take a moment to review the context, and then dig in to the words of Jesus themselves, making really sure we understand them, before we talk about what it looks like to apply these words to our lives.
1. Where We Are at in This Passage
So let’s begin by remembering the context. Jesus has been preaching the gospel of the kingdom and announcing the good news that the kingdom of God was at hand.
And He opened up the Sermon on the Mount by teaching about life in the kingdom. The kingdom that is already and not yet. Jesus’ disciples already have the good life based on what is not yet theirs, but which Jesus has promised in the future.
And then in verse 17, He said, “Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them” (Matthew 5:17). That’s a huge statement for a young man from the middle of nowhere to make.
And two weeks ago I suggested that Jesus needed to say this because this vision of the kingdom—of your best life later—sounded very different from what the people expected. It sounded like Jesus was setting the Bible aside, and so He has to say “No, I’m not setting it aside; instead, I am here to do everything it has been promising I will do.”
There are other reasons for Jesus to say these words, like the conflict with the scribes and Pharisees. People might have been surprised when John the Baptist called them a brood of vipers. These were the good guys, after all. After centuries of God’s people ignoring His law, these guys finally want to take it seriously.
But Jesus joined John’s team, not theirs. And in verse 20 Jesus said that if you want to get into His kingdom, your righteousness needs to be better than the scribes and Pharisees.
And again, that’s another huge statement for a young man from Nazareth to make. He’s taking on the whole establishment. But Jesus knows that for all of their appearances, these religious men are dead inside. And so starting in verse 20, Jesus teaches us that simply obeying the law of Moses on the outside isn’t enough for His kingdom. His disciples need to be righteous in their hearts.
And that points to a third and final bit of context here, which is this promise God had given to His people about the New Covenant. Last week Josh quoted Ezekiel 36 which spoke about the new heart God promised to give them. Another passage that speaks about this New Covenant is Jeremiah 31:
“Behold, the days are coming, declares the Lord, when I will make a new covenant with the house of Israel and the house of Judah, not like the covenant that I made with their fathers on the day when I took them by the hand to bring them out of the land of Egypt, my covenant that they broke, though I was their husband, declares the Lord. For this is the covenant that I will make with the house of Israel after those days, declares the Lord: I will put my law within them, and I will write it on their hearts. And I will be their God, and they shall be my people” (Jeremiah 31:31–33).
And in the Sermon on the Mount, Jesus is pointing us to that New Covenant. He is pointing us to our need to have God’s truth written onto our very hearts.
So that’s a bit of a sketch of the context here. We’ve got the new-sounding gospel of the kingdom fulfilling the Scripture, we’ve got the scribes and the Pharisees, and we’ve got the New Covenant.
And with all of that in the background, we’re ready now to take a look at verses 27 and 28 and review Jesus’ teaching on adultery and lust.
2. Jesus’ Teaching on Adultery and Lust
“You have heard that it was said, ‘You shall not commit adultery’” (Matthew 5:27). That’s what Moses said, and that’s what the scribes and the Pharisees said.
Adultery, if we need it defined, is being unfaithful to your spouse. It’s doing something with someone else that you should only do with the person you are married to.
And under Moses, and under the Scribes and the Pharisees, you could get by if you merely avoided adultery. As long as you didn’t actually do anything wrong with your body, you were fine.
But Jesus is not content with that standard of righteousness. He calls us to a truer and a better righteousness, a righteousness not just of the body but of the heart. And so He says, in verse 28, “But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart” (Matthew 5:28).
Like we’ve said already, these are familiar words, but I fear that their actual force might be blunted because of familiarity. We might assume too quickly that we know what these words mean.
We might assume that Jesus is simply saying, like I heard in so many of those youth group talks, “lust is as bad as adultery.”
But that is not just what Jesus is saying. What Jesus is saying is more shocking and more difficult than that. And in order to understand what He’s saying, we need to walk through the verse a bit more carefully and really pay attention.
So let’s begin with the word “lust.” “Everyone who looks at a woman with lustful intent.” What is lust? At its most basic meaning, it has to do with desire. Wanting something, often in a strong way.
Sometimes this word is used for wanting something good, like when Jesus said, “I have earnestly desired to eat this Passover with you before I suffer” (Luke 22:15). That’s the same word that is elsewhere translated “lust.” In that context, it’s a strong desire for a good thing.
Often the word is used for wanting something that we should not have. In the Greek Old Testament, the word for “lust” is used in the tenth commandment: “You shall not covet your neighbor’s house; you shall not covet your neighbor’s wife, or his male servant, or his female servant, or his ox, or his donkey, or anything that is your neighbor’s” (Exodus 20:17).
Very often in the New Testament the word is used in this way, to speak about desires for the wrong things. And sometimes the word is used very specifically used to speak about sexual desire. Wanting someone in that kind of a way. And it’s pretty clear that this is the way that Jesus is using the word here. He’s talking about wanting someone in that kind of a way.
But notice Jesus is not speaking simply about desire. He is speaking about looking to desire. “Everyone who looks at a woman with lustful intent.” This is one of those verses where I really appreciate the ESV, because it captures well the sense of the original language. The idea here is of a deliberate look for the purpose of desire; looking at someone in order to want them in that way.
One group of scholars translated these words this way: “the one who looks at a woman in such a way that desire for her is aroused in him.”1Walter Bauer, A Greek-English Lexicon of the New Testament and Other Early Christian Literature, rev. and aug. by William F. Arndt, F. Wilbur Gingrich, and Frederick W. Danker from the 5th edn. (Chicago, 1979), III.3.b, cited in Leon Morris, The Gospel according to Matthew, The Pillar New Testament Commentary (Grand Rapids, MI; Leicester, England: W.B. Eerdmans; Inter-Varsity Press, 1992), 118.
So notice here that Jesus is not saying “Everyone who looks at a woman has already committed adultery with her in his heart.” Under normal circumstances, if everyone is acting properly and dressing properly and so on, it should be normal for a man to look at a woman and vice versa and to just see a person, a person made in God’s image, someone with a history and a heart, and even to notice that they are good looking, and to not lust after them in a sinful way.
At the same time, please also notice that Jesus is not condemning every experience of sexual desire. He’s not talking about the experience where you’re going about your day and you happen to see someone and without invitation you experience an pang of desire.
What He is talking about is when you deliberately look back at that person in order to enjoy and feed and continue that desire. Martin Luther once said, “Dear brother, you cannot prevent the birds from flying in the air over your head, but you can prevent them from building a nest in your hair."2Martin Luther, Luther’s Catechetical Writings, Vol 1 (Minneapolis, MN: The Luther Press, 1907), 305.
Simply noticing someone and feeling the pang of desire might be like the bird flying over your head. Taking the second look, the deliberate look, in order to desire them—that’s letting the bird make a nest in your hair.
And Jesus says that whoever does this, whoever looks at a woman to lust after her, “has already committed adultery with her in his heart.”
Pay very careful attention to what Jesus is saying. He is not simply saying that lust is as bad as adultery. It’s more subtle, and more devastating, than that.
Jesus is saying is that lust is adultery in the heart. And so do you see it? Do you see what Jesus is doing? He is shifting the spotlight off of our behaviour and into our heart. He is showing that in His kingdom, merely having good behaviour is not enough. It doesn’t matter if you’ve never done anything bad. What matters is your heart. The people you’ve wanted. The things you’ve craved. The desires you’ve fed.
“For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false witness, slander,” He said in Matthew 15:19
In other words, sin does not start when you do something with your body. It starts in your heart. Sin occurs when you feed a desire in your heart for someone who is not yours to want, and look at that them in order to arouse and enjoy that desire.
So again, Jesus is saying so much more than “lust is as bad as adultery.” He is shifting the entire focus of righteousness from behaviour and onto the heart. It’s just like we saw last week. Unrighteous anger, in God’s books, is just as punishable as murder because it is murder as far as the heart is concerned.
And so it is with adultery. You have already committed adultery in your heart if you have looked at someone to lust after them. The sin itself is there, not in the fruit of your behaviour, but in the seed of your heart.
I used to work at a school, and we had a problem with mice. And there was one day where a mouse got caught in a trap, and dragged itself into a hole in a wall in the receptionist’s office where it died.
We didn’t know when that happened. We also didn’t know when exactly that mouse began to decompose. What we did know was that a few days later the receptionist had to move out of her office because the smell was so atrocious.
Some of you know exactly what rotting mouse smells like. It’s hard to describe how bad it smells, especially when it’s been mixed with gallons of air freshener that only make things worse.
Here’s the point of this illustration: the act of adultery is like that rotten smell. It’s out there in the open it’s awful and you can’t keep it a secret for very long. But looking to lust is like that little mouse with its foot in the trap breathing its last deep in the receptionist’s walls.
The Law of Moses said “don’t commit adultery.” “No stinky rotten smells.” And the scribes and Pharisees may have thought that as long as they didn’t actually touch that other woman they were fine. But Jesus sees into the dark corners of the walls of our heart, and He sees the mice lying there dead long before anybody else can smell them.
Jesus did not say “blessed are the well-behaved.” He said “Blessed are the pure in heart.” This is the righteousness that He requires in His kingdom.
And before I move on, I hope you can see that the principle here applies to so much more than lust and adultery. How many of you have turned on HGTV or flipped through Instagram or poured over the Cabela’s catalogue and wanted the things that you’ve seen?
How many times have we looked at other’s homes or possessions or lifestyles or families or vacations in order to want them in your heart?
How is that any different from what Jesus is describing here? It’s not. And it’s all sin, according to Jesus.
3. Jesus’ Command
Now at this point I want us to notice that so far, Jesus hasn’t actually told us to do anything. He’s simply told us that looking to lust is adultery in the heart.
The command that Jesus gives us actually comes in verses 29 & 30, which I invite you to look at now: “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 5:29–30).
And right here is where most scholars, most commentaries, and most study Bibles will say that Jesus is deliberately exaggerating. He’s using hyperbole. He is overstating things on purpose in order to make a point that staying faithful to your spouse is really important.
And maybe they’re right. But I’m not so sure. I’m not so sure that Jesus is exaggerating here. And the reason I’m not so sure is that His logic sounds rock-solid to me.
“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” (Matthew 5:29).
That makes perfect sense to me. You need a better righteousness than the scribes and Pharisees in order to inherit the kingdom of heaven. That means you need to be pure in heart. If you go through your life regularly indulging in lust, you’re not pure in heart. Which means that you won’t enter the kingdom. Which means that you will be thrown in to hell.
And if you believed that, and if there is a part of your body that is causing you to sin, you most certainly would cut it off and throw it away, because it would be way better to go through life without that part of your body than it would be to have a nice body for a short time and then burn in hell afterward.
Jesus’ logic is rock-solid, and it totally fits with the theme in the Sermon on the Mount about your best life later. It would be better to suffer now and enjoy eternal life later than to enjoy things now and enjoy eternal punishment later.
So I just really want that to sink in. Most of us treat sin so lightly, and we so easily dismiss Jesus’ words here, so we really need to feel the force of this.
God will punish the unrepentantly lustful in hell. This sin is so serious, and hell is so real, and Jesus’ standard of righteousness is so high, that literally taking a screwdriver to your eye would not be an overreaction if that eye really was causing you to sin.
And unless you get that, you haven’t really understood how radical and true the message of Jesus is. If chopping off your hand in your mind is too high of a price to pay for being a disciple of Jesus, than are you really sure that you are a disciple of the man who said “whoever does not take his cross and follow me is not worthy of me” (Matthew 10:38)?
Being a disciple means that we are literally ready to be nailed to a literal cross for the sake of our literal Jesus who will judge literal sinners in a literal hell for a literal forever.
And if you really believe that, then literally chopping off your hand is not unthinkable.
And now that I’ve said that, now that I’ve hopefully brought us here, I want to tell you all clearly that you should not chop off your hand or tear out your eye. Do not do that. Because they are not what is causing you to sin.
Just think about what Jesus said. “If your right eye causes you to sin… if your right hand causes you to sin.” Or in chapter 18, “If your foot causes you to sin.”
Does your right eye or your right hand or any other member of your body cause you to sin? Is that really where sin begins? What did Jesus say in verse 28? “Everyone who looks at a woman with lustful intent has already committed adultery with her in his eyes?” No, in his heart.
The sin is in the heart. You can pluck out your eyes and still lust. I read this week about Ray Charles, who was blind in both eyes and committed adultery again and again. I remember hearing a story years ago about a thief who had his hands cut off as a punishment for stealing, and he still kept on finding ways to steal.
Sin is not caused by your eyes or your hands or your feet but your heart. “But each person is tempted when he is lured and enticed by his own desire. Then desire when it has conceived gives birth to sin, and sin when it is fully grown brings forth death” (James 1:14–15).
So if that’s true, than what are we to do? Jesus’ command is that we must do whatever it takes to fight sin. And yet what if that sin is found in our heart? We can’t tear out our hearts and throw them away, can we?
“And I will give you a new heart, and a new spirit I will put within you,” said God through Ezekiel. “And I will remove the heart of stone from your flesh and give you a heart of flesh. And I will put my Spirit within you, and cause you to walk in my statutes and be careful to obey my rules” (Ezekiel 36:26–27).
Our hearts are the problem. And so we need a new one. And provision for a new heart is found in the New Covenant which Jesus came to bring.
This is what Jesus was talking about when He said “You must be born again” (John 3:7). And those who are born again, who have been given a new heart by the power of the Holy Spirit, know what purity of heart is like.
They know what it’s like to have freedom and victory over the sin, not just of adultery, but of looking to lust.
What Do We Do With This?
But if this is true, then what do we do about this? How do we put all of this together? Having seen the context and Jesus’ teaching on adultery and lust and now Jesus’ command that pushes us to see our desperate need for him, what are we supposed to do with all of this today?
And I’m going to suggest three statements that I pray help us apply this truth to our lives today in a way that really honours Jesus.
1. Disciples of Jesus Recognize Their Need for Atonement
If what Jesus says here is true—that sin starts in the heart, and that He sees and counts that sin—then we should recognize that we all stand condemned. If not on this sin, then on many other sins. Like anger, from last week. Or the countless other lusts and cravings and desires and greeds that we’ve fed.
We’re not okay. And if Jesus’ standards of righteousness are this high, than we need something to deal with our sin. Not just to pay for our behaviour but to cleanse our heart.
We need Jesus, the only perfectly pure man, to go to a cross and take all of God’s wrath for our sin, our lust, our anger, our coveting eyes, upon Himself and to perfectly pay for all of our sin.
And the good news is that He did this. “For if the blood of goats and bulls, and the sprinkling of defiled persons with the ashes of a heifer, sanctify for the purification of the flesh, how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to serve the living God” (Hebrews 9:13–14).
Someone must pay for the sin in our hearts. Either we will in hell, or we transfer them to Jesus, our sacrificial lamb, and trust His death to pay for them all. And I hope that this message leaves you looking to the cross and knowing that your only hope is Christ crucified as your substitute and your saviour.
So this is our first step this morning. Disciples of Jesus recognize their need for atonement, and they go to Jesus for that atonement.
2. Disciples of Jesus Recognize Their Need for a New Heart
Now there is a second point: disciples of Jesus recognize their need for a new heart. And if you need a new heart, then you need Jesus to give it to you. If you must be born again, then you must be born again.
And I just want to be really honest with you: when I hear about the statistics today of how many so-called Christian men are hooked on pornography, and go through year after year and even decade after decade of unbroken, unrepentant, unchanging sin, the question I cannot help but ask is how many of those so-called Christians have truly been born again.
How is it possible to have a new heart, to have the Holy Spirit himself living in you, to know and love Christ, and be repeatedly, unbrokenly indulging yourself in heart adultery?
I know two men who “struggled” with pornography for years, all the while going to church and looking like nice Christians on the outside, until the Holy Spirit brought them to repentance and showed them that they were not saved. They had not been born again. They were just good actors.
And then He moved in their hearts and made them feel the horror of their sin and their need for a saviour, and He gave them genuine repentance, and they looked away from themselves to Christ and they were born again—and their pornography addiction stopped in its tracks.
“Blessed are the pure in heart, for they shall see God” (Matthew 5:8).
Now I am not saying that everyone who struggles with the sin of lust is not a Christian. What I am saying is that genuine Christians have undergone a spiritual heart transplant and they will not be slaves to sin. They will never make peace with sin.
And what I am saying is that when we’re dealing with the sin of lust, especially habitual, continual, unrepentant lust, we need to bring these questions to the table: “Do you know Christ? Have you been born again?”
And if you are listening to this message this morning and your answer is “no,” then I invite you to come to Jesus. There’s no formula here. Just come to Jesus. Turn from your sin, leave it behind you, and come to Jesus who lived and died to save His people from their sin. And you know that I’d love to talk to you more about this if you want to get in touch.
3. Disciples of Jesus Take Their Sin Dead Seriously
There’s a third point for us to consider this morning. I just said that if you struggle with sin that doesn’t mean you’re not a Christian. Genuine disciples of Jesus will be tempted and yes, can give in to that temptation. Genuine disciples of Jesus can really struggle with certain sins.
But the key word there is “struggle.” So often when we say “I’m struggling with a sin,” we mean, “I feel guilty about it in church.” And that’s not struggling.
Genuine disciples of Jesus make war on their sin. We see that in this passage—that a genuine disciple of Jesus would gouge out their eye if that’s what it took to fight sin.
Now again, I’ve told you that gouging out your eye won’t help, so don’t do it. I don’t want to get sued here. But the idea here is that disciples of Jesus will take their sin seriously and will do whatever is necessary to kill it.
“For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live” (Romans 8:13).
Notice what Paul is saying there. We put to death the deeds of the body, our sin, not with knives or screwdrivers but by the Spirit, whose power is very connected to the Word of God.
And please also understand that as we do that, we’re not earning our salvation—we are proving our salvation. That’s how I take Jesus’ statements in verse 29 & 30 about being cast into hell. If you just continue on in unbroken, unrepentant sin, you are proving that you have not truly been saved. Whereas if you have truly been saved, have truly been born again, then you will be vicious with sin.
J.C. Ryle said, “He who would understand the nature of true holiness must know that the Christian is ‘a man of war.’ If we would be holy, we must fight.”3J.C. Ryle, Holiness.
This means fighting in our hearts where the desire starts. Fighting to believe the better promises of God instead of the cheap promises of sin. In my early 20s I memorized Psalm 84:11: “No good thing does he withhold from those who walk uprightly.” And I used that promise again and again as a sword against the temptation to reach out and grab for the forbidden fruit of lust.
Does this not also mean that we will be vicious with temptation itself? In the next chapter of Matthew Jesus will teach us to pray, “Lead us not into temptation” (Matthew 6:13). It won’t do you any good to gouge out your eye, but will do you a lot of good to be very careful with what you look at with your eyes.
This is why I’m careful, for example, with the movies I watch. How can I pray “lead me not into temptation,” and then deliberately sit down to spend two hours in front of something that I know will tempt me?
Parents, be very careful with giving your children and teens unrestricted access to the internet. Do not lead them into temptation by giving them what they are not able to handle.
And young adults and adults, be very careful with giving yourself unrestricted access to the internet. It blows me away how people will say they’re “struggling” with a sin like pornography and yet they will do nothing to lock down their smart phones, just having this wide open portal to temptation, and they will bring them with them into their bedrooms at night because, you know, buying a $12 alarm clock is going to break your bank.
That’s not struggling, folks. That’s just giving in. And that’s not good enough for disciples of Jesus. Disciples of Jesus will take their sin deathly seriously and they will make proactive war on it. “Be killing sin or sin will be killing you” said John Owen famously.
And this is true for whatever our sin is. Disciples of Jesus make proactive war on their sin, whether it’s lust or anger or greed or anxiety or grumpiness or dissatisfaction or whatever it is. And if you refuse to make war, you may very well just be proving that you are not a disciple of Jesus and that your destination is not the kingdom of heaven but the hell of fire. That is what Jesus has said and this is the warning that we must all take to heart today.
Now I know this message has been heavy hitting, but I hope that you feel the hope here. You do not need to stay under the power of sin. You can fight.
One of my greatest joys in pastoral ministry has been walking with people from patterns of habitual sin and into the freedom of purity. I’ll never forget sitting in Starbucks with one young guy who had been porn free for just a few weeks and was so enjoying his relationship with God as He spent time in His word and he told me that there was no way he was going to go back to his sin because there is no way he was going to give up what He was enjoying now.
Whatever you’re sin is, whatever your temptation is, you are not helpless. If anyone is in Christ, he is new creation (2 Corinthians 5:17). Your sin may haunt your steps but you’re not a slave to it any more. You’ve been born again, the sword of the spirit is in your hand, and in Christ you can and you must make war.