Be Killing Sin

Matthew 5:27–30 — Sermon on the Mount

I can't speak for you, but I would imagine that many of us walked out of here feeling the weight last week - the anger, the contempt, the relationships we've left unreconciled. There wasn't a lot of reprieve. I felt it too. And I'll tell you up front: this morning is not going to start by lifting that weight off you. We're going to add to it first. Because Jesus moves from the sixth commandment to the seventh, and if you thought Jesus' teaching that the 6th commandment isn't just about the physical act of murder, but murder in the heart (Matthew 5:21–22), wait until He gets to the 7th.

But stay with me through the whole arc this morning, because where we land today is the weight that you may have carried in today isn't going to get any better until it gets a little worse.

Stand with me. Matthew chapter 5, verses 27 through 30.

✦ "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)

You may be seated. Let's pray.

I. The Wrong Question

So, here's the pattern we set up last week. "You have heard that it was said... but I say to you." (Matthew 5:27–28) Every time, Jesus takes a command that we, and the religious leaders in Israel are familiar with, but what's true of us today was true of them too. We're tempted to define the law in a way that protects us. We’re tempted to see the law and say, ”God is most concerned with the biggest sins, not the picadillo.”

When we read the seventh commandment, You shall not commit adultery, (Exodus 20:14) we could keep that — technically — our whole life. Never touch a man or a woman who isn't our spouse. Stay on the right side of the line. Anyone who can keep themselves from the physical commission of the act. We saw this with murder; we see it again with adultery. Anyone who could keep themselves from the physical commission of the act could count themselves righteous. A narrow definition of sin. A broad definition of righteousness. That keeps us very comfortable.

And Jesus says no. Everyone who looks at another person with lustful intent has already committed adultery with them in their heart. (Matthew 5:28)

This is the idea I want to dive a little deeper into this morning. The one who seeks only to keep the technical line is asking a question. The question is: how far can I go before I've sinned? Where's the line, so I can get as close to it as possible and still be safe? That's the Pharisee's question. That's, in many cases, our question. What can I get away with?

Jesus does not answer that question. He destroys it. He says the line was never at the physical commission of the act — it was in the heart all along.

▸ The question is not "is this a sin?" The question is "what glorifies God?"

It’s the shift from the negative command, don’t do this, to the positive command, Do this.

In what feels like another lifetime, I had the incredibly exciting opportunity of teaching 18-year-old students, fresh out of high school, how to operate what was essentially a Volkswagen Bug with wings. When I would take them up for the first several lessons, they would shadow me on the controls, but I would fly us up to 3000 feet. I would set up the Cessna 172 that we were flying straight and level. I would tell them to take a mental snapshot of the visual queues. It changed slightly every time, but it was largely the same. You would hold the horizon right on the dashboard, or 1" above, or 1" below, but I would set it up for them first because there are thousands of wrong ways to do it, but there is a right way. This is true any time we teach. Any time we learn. It takes a lot longer and a lot more effort to learn all of the things you're not supposed to do, than when you focus on the thing you are supposed to do.

And back to our question, those are two completely different universes, and I think Paul lived in the second one when he says in. "All things are lawful for me, but not all things are helpful" 1 Cor 6:12 — and then he takes that exact principle, in that exact chapter, straight to the body and to sexual sin, and he lands it here: "glorify God in your body." Whatever you do, "do all to the glory of God." 1 Cor 6:20 That's not the line-question. That's the glory-question. We also see this clearly in that WSC Q1 that we reference all the time. "What is the Chief end of man? To find the line and stomp on it our whole way to glory? No. "To glorify God and to enjoy Him forever". Or Piper's rendition, "To glorify God BY enjoying Him forever."

So before we even get to the severity of Jesus' words, we need to be asking the right question. If you came in this morning wondering how much can I look at, how close can I get, is it technically adultery — Jesus is not going to give you a number and a yardstick. He's going to point at your heart.

II. Mortification, Not Mutilation

And then He says something that, no matter how many times you've heard it, should leave you stunned.

If your right eye causes you to sin, tear it out. If your right hand causes you to sin, cut it off. (Matthew 5:29–30)

You guys know those labels on your coffee lid that say, "Warning: Contents may be hot." or the one that's on all of your plastic bins that says not to close the lid while your kid is in it? Those are all there primarily because of lawsuits, but clearly because there is at least a handful of people that need that warning.

I'm going to give you one of those warning labels this morning because there was a man named Origen, who lived in the third century, clearly more zealous than wise, who read this verse and a verse in Matthew 19 and made himself a eunuch. The church, at one of the councils, later had to formally forbid that. So let's be clear, that is not what Jesus is asking for.

The distinction here, then, is pretty important. Jesus is not commanding mutilation. He is commanding mortification. Those are not the same thing. Mutilation is cutting the body. Mortification is putting the sin to death.

So watch how concrete Jesus actually gets — because mortification is not vague spiritual ambition, it's specific and ruthless. The argument runs from the eyes to the heart: heart-adultery is fed by eye-adultery. So you fight the war on the front line — at the eyes — before the imagination is ever given the fuel. Job knew this, ✦ "I have made a covenant with my eyes; how then could I gaze at a virgin?" (Job 31:1) He didn't pray Lord, fix my heart after the fact. He made a covenant at the gate, before the moment ever came.

That's mortification. And here's the way to actually hear the command: if your eye causes you to sin, then live as though you had no eye for that thing. Don't look. If your hand causes you to sin — the thing you do — then live as though you had no hand for it. Don't do it. If your foot — the place you go — then live as though you couldn't walk there. Don't go. That's it. That's what "tear it out" means. Not a knife, a refusal so total it's as if the member were gone.

Now — and this is where I have to be careful, because everything we've built over these months hangs on it. If I stop right here, I've just handed you a religion of willpower. Try harder. Cut more off. White-knuckle your way to purity. And that is a lie, and it will crush you, and it is the very thing Jesus has been tearing down since we began with anger last week. We do not have the power to earn glory by our own merit.

So where does the power come from? Not from you. ✦ "If by the Spirit you put to death the deeds of the body, you will live." (Romans 8:13) By the Spirit. John Owen wrote a whole book on that one verse, and you know the line — "Be killing sin or it will be killing you." That's the relentlessness. This is daily war, not a one-time decision. But Owen is just as clear: the power to kill it is not native to you. It's by the power of the Spirit.

And listen to where Paul puts the command. Turn with me to Colossians 3 — ✦ "Put to death therefore what is earthly in you: sexual immorality, impurity, passion, evil desire." (Colossians 3:5) There's your mortification, naming this exact sin. But read what comes before the command: "If then you have been raised with Christ... you have died, and your life is hidden with Christ in God." (Colossians 3:1, 3) The command comes second. The reality comes first. You put sin to death because you've already been raised — not in order to get raised. ✦ "Those who belong to Christ Jesus have crucified the flesh with its passions and desires." (Galatians 5:24) The crucifying flows out of the belonging. You don't mortify sin to earn your place. You mortify sin because your place is already secured, and now you're free to fight without your eternal standing before God riding on whether you win today.

That's why Jesus can be this severe. It is better to lose one of your members than that your whole body be thrown into hell. (Matthew 5:29) He means it. The stakes are eternal. (And note — our text says "lose a member" versus the whole body in hell; it's the parallel in Mark 9 and Matthew 18 that adds "better to enter life maimed." (Mark 9:43–47; Matthew 18:8–9) Same teaching of Jesus, fuller picture: it's better to walk into eternal life crippled than to march in whole and walk right past glory, and into hell.) The severity is real. Judgement is real. Hell is real. And the man whose acceptance depended on his own success against lust could never face this judgment honestly — he'd hide, minimize, lie to himself. But you, whose life is hidden with Christ, can name your sin out loud and go to war on it without fear. Because losing a battle can't cost you the kingdom.

III. The Maiming the World Won't Understand

If, then, we are to take Jesus at His word, that means obeying His commands is going to cost you something visible. Jesus says you may end up, in His words, maimed. And here's what that means for us today: you are going to have to cut things out of your life that mean the end of a season, the end of a friendship, the end of something that, if you're honest, you really enjoy, and people are going to think you're strange for it.

You may choose not to see a movie or a Netflix special that everyone's talking about. You may leave a conversation. You may choose not to be a part of the town square that's supposed to keep us all connected. And someone will look at you like — you didn't see that? You're not on there? What are you, that old-fashioned? Weird? Narrow-minded? And maybe by the world's measure, you'll be a little bit maimed. Culturally amputated. The only question is whether, for what you gain, you're willing to bear what you lose.

I have some things myself that I've cut out of my life. There are some things that our family either does or does not do that don't make sense to some of my old friends or some of my family members. Those things look different for all of us. It depends on what makes you struggle. What tempts you. We talked about this is Romans, that it's our responsibility not to cause another brother to stumble when our convictions are different (Romans 14:13–23), so we can respect the boundaries and guardrails that other people in our life have set without feeling the obligation to take them on ourselves.

And for some of you — especially the younger ones in here — the cost feels even more weighty. Because the world has told you that you have to build a presence. Curate yourself. Make yourself into something people will follow, or you don't matter. And to walk away from that feels like walking away from your own significance.

So, if you're listening to me right now trying to justify that thing that you know is harmful to you, your physical health, your emotional health, most importantly, your spiritual health, gouge it out and throw it away. Paul says: ✦ "Do not be conformed to this world, but be transformed by the renewal of your mind." (Romans 12:2) And look how that command opens — "by the mercies of God." (Romans 12:1) You don't refuse to be conformed in order to earn mercy. You refuse because mercy has already remade you. ✦ "If anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come." (2 Corinthians 5:17) You have been radically changed. So you live a radical life — not to become somebody worthy of Jesus' salvation, but because in Christ, the Father has already said that you are.

You can afford to lose the brand. You can afford to miss the feed, the photos, the being-in-the-loop. Because — and we're only a chapter early on this one — ✦ "where your treasure is, there your heart will be also," (Matthew 6:21) and your treasure is somewhere moth and rust and trending cycles can't touch.

IV. In Full Color

Some of you are feeling the weight getting heavier. Last week was heavy, this week we piled on — adultery in the heart, hell, cut it off. And there's a voice that says the gracious thing would be to ease that weight a little. The problem with that is we all love to be comfortable. We all want our wounds nursed. We want to be told that life is hard, but it'll all be okay because you can do it.

The hard part is that you can't do it. Not on your own. You need more of Jesus and less of you. One of the ways Jesus brings us to that revelation is through our own sin.

▸ The deeper you see your sin, the richer His grace becomes.

I used to give an image to explain what salvation was like for me. It felt like I had been watching the movie of my life, but there was no audio, and the subtitles were in a foreign language. When my eyes were unblocked and my ears were unstopped, it was like someone turned the subtitles to English, and it all made so much more sense.

Early in my walk, it felt like I was now watching the movie, and I understood the subtitles, but it was still an old black-and-white set, low-resolution, fuzzy movie, and I had made a kind of peace with it. Then someone turned on the full picture — full color, full resolution — and for the first time I saw my sin in all its actual depth, exactly the way the God who made me and loves me saw it. My first instinct is that the picture is unbearable. But what actually happens: when the sin comes into full color, so does the mercy. You cannot see the height of what you've been given until you've seen the depth of what you were saved from.

Conviction isn't the enemy of grace. It's the resolution that makes grace even more beautiful.

Paul does this in one breath. He lists the sins — the sexually immoral, the adulterers, all of it — the very people this passage is about. And then: ✦ "And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ." (1 Corinthians 6:11) Washed. Past tense. Done.

Now I'm going to move quickly here, because we've laid this groundwork together over the last couple of months and I'm trusting you to carry it.

We've read this many times — ✦ "For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God." (2 Corinthians 5:21) Your sin reckoned to Christ; His righteousness reckoned to you. And I want you to feel the active side of that, not just the pardon. It is not only that your slate is wiped — that would just make you neutral, a blank page. It's that His perfect record is credited to you. This is where R.C. Sproul, in his commentary on this very chapter, says something that stopped me cold: he tells a room that those who are no longer pure can be made pure again by their Savior. I'll be honest — my first reflex was to argue with it. That's not how it works. What's done is done. You just keep it from getting worse from here. And I was wrong, and being wrong exposed how small my view of the cross had gotten. Because that instinct treats the blood of Jesus as if it can stop the bleeding but not heal the wound. It diminishes the finished work. The active obedience of Christ doesn't just cancel your record — it gives you His. Machen, dying, sent a telegram to a friend: "I'm so thankful for the active obedience of Christ. No hope without it." No hope without it. That's the whole thing.

So here's the tension, and we've named it all year — Luther's phrase: simul iustus et peccator. At the same time righteous and a sinner. As to my standing before God — fully, really righteous, clothed in Christ. As to the corruption still in me — still a sinner, still at war. Both true, but one of these is a temporal reality, and one of these is an eternal reality. That's your whole Christian life. It's the already and the not yet sitting in you.

We tend to think God sees us one way — redeemed, in Christ — but the real truth is the guilt and shame that we still feel. We treat the feeling as more real than the verdict. Think about what that actually claims if we count the sin in us as more real than the justification declared over us by the Father in the name of the crucified and ascended Jesus. It claims there's a reality God is not sovereign over. A reality truer than what God Himself declares. There is no such reality. When God says righteous over you in Christ, that is the most true reality that exists. It is the truest thing about you — truer than your worst sin, truer than how you feel right now.

And let me be clear here. Sin grieves God. There is no sin that God does not know, no sin that does not see, and no sinner that is not in need of God's grace. But the verdict isn't a label slapped on a stranger. It rests on union — you are really joined to Christ, so His righteousness is really yours. You, believer in Jesus, have received a righteous judgment from your father.

So what happens to the weight? The conviction stays — the law still indicts, the Spirit still convicts, and that does its work; that's what drives the mortification. But the condemnation is gone. ✦ "There is therefore now no condemnation for those who are in Christ Jesus." (Romans 8:1) Guilt as conviction does its job and leads you to the cross. Guilt as condemnation has been utterly removed, in full, at the cross. So the weight you've been carrying this morning — take it to the cross. There is forgiveness, there is salvation, there is boundless love waiting for you to repent of your sin, turn away from your old ways, and believe the Gospel. Give your life to Him as a response to Him as a living sacrifice, holy and acceptable to Him (Romans 12:1).

V. Behold Your God

Let me close where all of this actually starts. The garden.

Before there was any sin to forgive, before there was a single act of mercy, God was worthy of worship. Adam and Eve didn't worship God because He'd pardoned them. Before the fall, there was nothing to pardon. They worshiped Him because He is God. And that's still the center of our worship. ✦ "Worthy are you, our Lord and God, to receive glory and honor and power, for you created all things." Rev. 4:11. That's the song before the fall ever happened. He is worthy because of who He is.

And then sin enters, Jesus goes to the cross, and heaven adds a second song — ✦ "Worthy are you... for you were slain, and by your blood you ransomed people for God." (Revelation 5:9) The mercy doesn't make Him worthy. He was always worthy. The mercy gives us another reason to sing. We have seen the attributes of the God that we worship with even more clarity, even more resolution.

So don't walk out of here this morning worshiping God because He let you off the hook. Worship Him because He is God — and then, on top of that, we sing the Lamb's song, because the God who needed nothing from you stooped down and washed you anyway. That's not a lighter weight than you came in with. It's a heavier God's eternal glory.

The already: you are washed, justified, righteous in Christ — right now, in this room, this is your present reality. The not yet: one day you'll see Him face to face and the war will be over for good. Only one truth about you will remain. We live right in the middle of that. Maimed, maybe. Broken. In need of His grace every day, every moment. But as we come to the table now, we are reminded. He has given all of Himself to us, and we are fully His. Now, in that same reality where God declares us righteous, we fellowship with Him who gave His body as this bread, and His blood as this wine.

Let's pray.

Scripture Reference List

Sermon text

Exodus 20:14 — "You shall not commit adultery" (the seventh commandment)

1 Corinthians 6:12 — "All things are lawful for me, but not all things are helpful"

1 Corinthians 6:20 — "glorify God in your body"

1 Corinthians 10:31 — "do all to the glory of God"

II. Mortification, Not Mutilation

Matthew 5:29–30 — "If your right eye causes you to sin, tear it out…"

Matthew 19:12 — the verse Origen also misread

Job 31:1 — "I have made a covenant with my eyes…"

Romans 8:13 — "If by the Spirit you put to death the deeds of the body…"

Colossians 3:5 — "Put to death therefore what is earthly in you…"

Colossians 3:1, 3 — "raised with Christ… your life is hidden with Christ in God"

Galatians 5:24 — "Those who belong to Christ Jesus have crucified the flesh…"

Matthew 5:29 — "better to lose one of your members…"

Mark 9:43–47; Matthew 18:8–9 — "better to enter life maimed/crippled"

(John Owen, — not Scripture)Of the Mortification of Sin

III. The Maiming the World Won't Understand

Romans 14:13–23 — not causing a brother to stumble; differing convictions

Romans 12:2 — "Do not be conformed to this world, but be transformed…"

Romans 12:1 — "by the mercies of God"

2 Corinthians 5:17 — "If anyone is in Christ, he is a new creation…"

Matthew 6:21 — "where your treasure is, there your heart will be also"

IV. In Full Color

1 Corinthians 6:9–11 — the vice list and "And such were some of you. But you were washed…"

2 Corinthians 5:21 — "For our sake he made him to be sin who knew no sin…"

Romans 8:1 — "There is therefore now no condemnation for those who are in Christ Jesus"

Romans 12:1 — "a living sacrifice, holy and acceptable to Him"

(R.C. Sproul commentary on Matthew; J. Gresham Machen's telegram; Luther, — not Scripture)simul iustus et peccator

V. Behold Your God

Revelation 4:11 — "Worthy are you, our Lord and God… for you created all things"

Revelation 5:9 — "Worthy are you… for you were slain… you ransomed people for God"

(cf. Luke 22:19–20; 1 Corinthians 11:23–26 — the Lord's Table)