Of the Mortification of Sin in Believers
A modern-English rewrite of John Owen's 1656 treatise, based on his original text
Preface & Chapters 1–3
Preface
A quick note before we start: Owen uses the word "mortification" throughout this book, and we've kept it rather than swapping it out. It's an old word for "killing" or "putting to death" — here, killing sin's power in your life. We kept it because it's the book's central idea, and Owen means something stronger and more deliberate than "resisting" or "managing" sin — he means actively putting it to death. You'll get used to it fast.
To you, the reader,
Let me tell you honestly why I decided to publish this.
The main reason is what I see happening in the church today. Christians are living in a time of relative peace, and they're also divided against each other. Neither of those things is helping them. When I look at the hearts and lives of people who claim to follow Christ, I see people who aren't ready to fight temptation. If this book does nothing more than push people to actually examine their lives — and gives them clearer direction on how to do that — I'll count this work worth it.
There's a second reason, too. I've watched other teachers give dangerous advice on this exact subject. They don't understand the gospel or what Christ's death actually accomplished, so they end up putting a heavy, exhausting burden back on people — telling them to defeat sin through their own effort and willpower. That's a weight neither they nor anyone before them could ever carry. It isn't the gospel's way of dealing with sin at all — not in what it's rooted in, not in how it works, not in what it produces. And what it produces is predictable: people who are self-righteous, superstitious, and constantly anxious in their conscience.
What I've written here is offered humbly. I hope it lines up with both the Spirit and the plain teaching of the gospel, and with the real experience of people who actually know what it means to walk with God under his covenant of grace. Even if this particular book isn't the one that does it, believers desperately need something like it — something that will move this work of gospel-mortification forward in their hearts, and set them on a path where they can actually find rest for their souls.
I should also mention a few personal reasons. I had preached on this subject already, and God used it — people were genuinely helped. Several of them urged me to publish what I'd preached, with whatever changes I thought necessary. That encouraged me. It also reminded me of a debt I owed some dear friends: I'd promised them a book on communion with God, and years had passed without delivering it.1 I couldn't pay that larger debt yet, but I thought I could at least offer them this shorter work in the meantime — like paying interest while the real debt waits. On top of that, I'd spent a good deal of time caught up in public theological controversies, and it seemed right to also produce something of a different kind — something written not because I had to, but because I wanted to.
For all these reasons, this short book now stands before you. I can honestly say that the deepest desire of my heart, and the main purpose of my life in the calling God has placed me in, is this: that mortification and wholehearted holiness would grow — both in me and in everyone else — for the glory of God, so that the gospel of our Lord and Savior Jesus Christ would be made beautiful in every way. If this little book helps even the least significant believer move toward that goal, I'll consider it an answer to the weak prayers of its very unworthy author.
John Owen
Chapter 1: Romans 8:13 Explained
Everything I'm going to say in this book stands on one verse: Romans 8:13.
"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, ESV)
I want to build this whole discussion on that verse, so let's slow down and actually look at what it's saying before we go any further.
The setting
Right before this verse, Paul has just finished explaining that we're justified by faith — that everyone who trusts in Christ is fully forgiven and stands before God with nothing held against them (Romans 8:1–3). Now he turns a corner. Having explained what God has done for us, he starts explaining what that should produce in us: holiness.
And here's the warning he gives on the way there: "if you live according to the flesh you will die" (Romans 8:13, ESV). I'm not going to unpack every angle of what "living according to the flesh" or "dying" means here — I only need enough of it to make sense of the second half of the verse, which is where we're headed.
Five things packed into this one verse
If you look closely, Romans 8:13 is actually making five separate points at once:
1. A command — "put to death the deeds of the body."
2. Who it's for — "you." (Not everyone. Specifically believers.)
3. A promise attached to it — "you will live."
4. Who actually does the work — "through the Spirit."
5. A condition wrapped around all of it — "if..."
Let's take these one at a time.
1. The "if" is about certainty, not doubt
When Paul says "if," he's not saying "maybe you'll do this, maybe you won't, we'll see." He's already told these same readers, one verse earlier, that "there is therefore now no condemnation for those who are in Christ Jesus" (Romans 8:1, ESV). Their standing with God isn't in question.
Instead, this is the same kind of "if" you'd use with a sick person: "If you take this medicine, you'll get better." You're not doubting whether they're allowed to get better — you're pointing out a sure connection between the medicine and the healing. That's exactly what Paul is doing here. He's not describing a cause producing an effect (eternal life isn't something we earn — it's a free gift, Romans 6:23). He's describing a means that leads to an end God has already promised. Put simply: put sin to death, and you will live. That connection is certain — and it's the main reason this command carries real weight.
2. Who this is for
The word "you" here is aimed at believers specifically — people who already have no condemnation (v. 1), who are no longer ruled by the flesh but by the Spirit (v. 9), who have already been made alive by that same Spirit (vv. 10–11). This isn't a command for outsiders trying to earn their way to God. Piling this duty on people who don't yet know Christ just produces self-righteousness and empty religion — that's what happens whenever people who don't understand the gospel try to enforce it anyway.
So here's the main thesis of this entire book, stated plainly:
Even the best believers — people who are completely and permanently free from sin's power to condemn them — still have to spend their whole lives putting sin's ongoing power to death.
Being forgiven doesn't mean sin stops fighting you. It means you now have every reason and every resource to fight back.
3. Who actually does this work
Paul says "through the Spirit" — not through willpower, not through self-discipline alone, not through gritting your teeth harder. This is the Holy Spirit's work: the same Spirit who lives in believers, gives them life, and prays for them.
Every other way of trying to kill sin — through sheer effort, through rules you invent yourself, trying to make yourself right with God by your own strength — is a dead end. That approach, dressed up in different forms, is the essence of every false religion there's ever been. It cannot work, because it was never designed to.
4. What "put to death the deeds of the body" actually means
This phrase has three parts worth unpacking: what "the body" means, what "the deeds of the body" means, and what "putting to death" means.
"The body." This isn't just talking about your physical body. Paul uses "the body" here the same way he's already been using "the flesh" throughout this chapter — as another name for the sin that still lives inside every believer. Elsewhere he calls this same thing "the old self" (Romans 6:6). It's the corruption still present in us, the part of us still bent toward sin, even after we belong to Christ.
"The deeds of the body." This means the actions and fruit that sin produces — both what shows up on the outside (the sins other people can see) and what's happening underneath, in the desires and impulses that give rise to them. Paul's point is to go after sin at the root, not just trim the branches. You don't just deal with the visible sin; you deal with what's producing it.
"Put to death." This is a deliberate word picture: killing something. To kill a living thing is to strip it of all its strength and power, so it can no longer act. That's exactly the picture here. Indwelling sin is described like a living enemy — Paul elsewhere calls it "the old self" — with its own kind of cunning, strength, and staying power. That enemy has to be killed: stripped of its power to produce what it wants to produce.
In one sense, this is already done. When Christ died, sin's ultimate claim on us died with him — that's the meaning of being "crucified with Christ." And the moment you were made new in Christ, something was planted in you that's fundamentally opposed to that old sinful nature. But — and this is the whole point of this book — that doesn't mean the fight is over. What's true positionally has to be worked out practically, a little more each day, for the rest of your life.
So here's what Paul is actually calling believers to: make sure indwelling sin never regains enough strength to produce the sinful actions it wants to produce. That's a daily, lifelong duty.
5. The promise: real life
The promise attached to all this is simple: "you will live." This is the opposite of the death Paul warned about a moment earlier — "if you live according to the flesh, you will die."
This promise isn't only about eternal life, though it includes that. It's also about the quality of life you get to experience right now — not the bare fact that you're spiritually alive (every believer already has that), but the joy, comfort, and strength that comes with it. Paul uses similar language elsewhere: "for now we live, if you are standing fast in the Lord" (1 Thessalonians 3:8, ESV) — meaning, "now my life actually feels like something good; now there's joy in it." That's the promise here too: live this way, and you'll experience a good, strong, comforting spiritual life now — and eternal life to come.
Which leads to the whole point of this chapter, stated as simply as I can put it:
How strong, joyful, and alive your walk with God feels depends directly on whether you're putting the deeds of the flesh to death.
That's the foundation everything else in this book is going to build on.
Chapter 2: The Duty of the Best Believers
Here's the thesis I laid out at the end of Chapter 1, and now I want to back it up:
Even the best believers — people completely and permanently free from sin's power to condemn them — still have to spend their whole lives putting sin's ongoing power to death.
Even mature believers have to keep fighting
Paul writes, "Put to death therefore what is earthly in you" (Colossians 3:5, ESV). Who's he talking to? Not new converts. Not people who are struggling to get started. He's talking to people he's just described as raised with Christ, dead with him, and destined to appear with him in glory (Colossians 3:1–4). In other words: mature, secure, deeply established believers. And his instruction to them is still: mortify. Make it your daily work. Never take a day off from it. Be killing sin, or it will be killing you. Being united with Christ doesn't excuse you from this fight — it's what qualifies you to win it.
Jesus makes a similar point with a different picture: even the branches that are already bearing fruit get pruned, "that it may bear more fruit" (John 15:2, ESV). Growth doesn't mean you stop needing to be cut back — it means you get cut back more carefully, and more often, for as long as you're alive in this world.
And Paul says this was his own daily practice, even at the height of his ministry: "I discipline my body and keep it under control" (1 Corinthians 9:27, ESV). If this was the business of Paul's life — a man who'd seen more of God's grace and glory than almost anyone — none of us gets to claim an exemption.
So why does this never stop being necessary? A few reasons.
1. Sin never fully leaves you in this life
There's no point in your life on earth where sin's presence in you gets down to zero. I'm not interested in getting into arguments about theoretical sinless perfection — in my experience, the people most confident they've reached it usually just mean they've stopped being able to tell good from evil anymore, not that they've actually stopped sinning. For the rest of us, who take Scripture at its word, indwelling sin sticks around in some measure for as long as we're here. Paul himself refused to claim he'd "already attained" (Philippians 3:12). Our "inner self is being renewed day by day" (2 Corinthians 4:16, ESV) — which only makes sense if there's still an old self being worn down, day by day, alongside it. As long as sin is present, it has to be actively resisted. Someone assigned to defeat an enemy doesn't get to stop fighting just because the enemy is still breathing.
2. Sin isn't just present — it's active
This is the part people miss. Sin doesn't sit quietly waiting to be provoked. It's constantly working, whether you notice it or not — and it's usually working hardest exactly when it looks the quietest. Paul describes an internal war: sin's law fighting against his mind (Romans 7:23). James says the same: our internal desires are actively "at war within" us (James 4:1, ESV, cf. James 4:5). Every day, in every choice, sin is doing one of three things: pulling you toward evil, holding you back from good, or quietly pulling your heart away from closeness with God. If sin is always active, and you're not always resisting it, you will lose ground. There is no truce available in this fight — not even for a day.
3. Left unchecked, small compromises grow into ruinous sins
Paul lists what happens when sin is simply allowed to run its course — sexual sin, hostility, idolatry, addiction, and more (Galatians 5:19–21). Here's the pattern worth understanding: every sinful impulse, left to itself, aims for the extreme version of itself. A wandering thought would become full-blown sin if it could. A moment of envy would become open hatred if nothing stopped it. Sin rarely announces this ambition up front — it starts small, modestly, almost reasonably — and that's exactly what makes it dangerous. It gets a foothold quietly, then pushes further, a little at a time, without ever feeling like a big jump. That's what Scripture means by being "hardened by the deceitfulness of sin" (Hebrews 3:13, ESV) — you don't usually fall off a cliff; you get walked off the edge one small, unnoticed step at a time. The only thing that reliably interrupts this pattern is mortification — going after sin at the root, every single day, before it has the chance to build momentum.
4. God gave you the Spirit specifically to fight this battle
This is actually one of the main reasons the Holy Spirit and your new nature were given to you in the first place — so that you'd have something inside you capable of resisting sin. Paul says it goes both directions: not only do "the desires of the flesh" work against the Spirit, but "the desires of the Spirit are against the flesh" too (Galatians 5:17, ESV). You weren't left defenseless. Refusing to use that gift — coasting instead of actively engaging the fight — isn't neutral. It's neglecting the exact weapon God armed you with against your greatest enemy. Grace, like any gift, is meant to be used. Leaving it unused while sin runs free is an insult to the God who supplied it.
5. Neglect doesn't just stall your growth — it reverses it
Here's what's really at stake. Paul says that even while his body was wearing out, his "inner self" was "being renewed day by day" (2 Corinthians 4:16, ESV). Neglect this duty, and you get the exact opposite: your inner life withers while sin gets stronger. Grace, like anything living, needs to be exercised or it decays. Believers who stop actively fighting sin don't just plateau — they can watch formerly tender, humble, zealous faith slowly curdle into something cold, worldly, and compromised, to their own grief and everyone else's confusion. There's no truly neutral gear here. You're either gaining ground or losing it.
6. This is simply what it means to grow as a believer
Scripture calls you to keep "perfecting holiness" (2 Corinthians 7:1), to keep growing in grace, and to let your inner self be "renewed day by day" (2 Corinthians 4:16, ESV). None of that happens automatically. It happens through the daily mortifying of sin. Don't fool yourself into thinking you're making spiritual progress while leaving your besetting sins untouched. Whoever isn't actively working against sin isn't making progress toward anything — they've simply made peace with the thing they were supposed to be fighting.
The bottom line
Yes, sin's ultimate power over you was already broken at the cross. Yes, something new and opposed to sin was planted in you the moment you were saved. But that doesn't mean the war is over — it means you now have everything you need to keep fighting it, every day, for the rest of your life. That's simply what it looks like to be a believer this side of heaven.
A warning: what happens when believers stop taking this seriously
I want to pause here and say something that troubles me. I see a lot of Christians today who have plenty of Bible knowledge, plenty of spiritual gifts, plenty of impressive-sounding talk about grace — and almost no real fruit of mortification to show for it. That gap is dangerous, and it does damage in two directions.
First, it damages you. Whatever you might claim, if you're not actually fighting sin, it's because deep down you've stopped taking sin seriously — at least the "ordinary," everyday kind. And that's the real danger zone: a heart that has learned to swallow its own sin without so much as a wince. Once someone gets comfortable using grace and forgiveness as an excuse to stop resisting sin, rather than a reason to fight it harder, they're standing right on the edge of turning God's grace into a license — and that road rarely ends well. Honestly, this describes the path of most of the people I've watched walk away from the faith entirely. They started well, but once genuine conviction faded and daily obedience felt like a burden without a clear reason behind it, they leaned on "grace" to excuse what they no longer wanted to fight. And that excuse-making, once it takes hold, moves fast.
Second, it damages the people around you. An unmortified life quietly hurts others in two ways. It hardens them — because when they look at professing Christians who look "fine" on the outside despite obvious compromise, it teaches them that this level of compromise must be acceptable, so they lower their own guard to match. And it deceives them — because it teaches them that clearing a fairly low bar is enough to call it faithfulness, when in reality they might be matching your outward reputation while still falling far short of real life in Christ.
More on both of these later — but I wanted this concern on the table early, because it's exactly why this book exists.
Chapter 3: The Spirit Alone Can Do This Work
Here's the second major principle of this book:
The Holy Spirit alone is sufficient to kill sin in you. Every method that leaves him out accomplishes nothing — no matter how impressive it looks.
📝 TRANSLATOR'S NOTE (not part of Owen's text):* In this section, Owen is specifically pushing back against certain medieval and 17th-century Catholic monastic practices — strict fasting, self-imposed suffering, elaborate vows and rituals — that were being promoted as ways to defeat sin through sheer human effort and religious performance. He's not writing about Catholics in general. Below, we've kept his actual argument rather than his specific historical target, because the underlying mistake he's describing shows up constantly today, in every tradition: trying to kill sin through willpower, rule-keeping, and religious effort while leaving the Holy Spirit out of the picture entirely.
Why self-effort religion always fails
No matter how intense or sincere the effort, self-powered religious performance cannot kill sin. People have tried it for centuries — punishing rules, harsh self-denial, strict routines, all aimed at defeating sin through sheer discipline. And it never actually works, for two reasons.
First, some of these methods were never things God actually commanded. They're human inventions, dressed up as spiritual disciplines. Whatever effort you pour into a method God never designed for this purpose is effort spent chasing something that was never going to deliver.
Second, even the methods God does command — things like prayer, fasting, and Scripture meditation — get misused when people treat them as the source of the power itself, rather than as tools the Spirit works through. These practices are meant to be streams, not the fountain. Used rightly, in dependence on the Spirit, they're genuinely valuable. Used as a self-powered system — "if I pray enough, fast enough, follow the routine closely enough, sin will die" — they can keep someone perpetually busy with religious activity while sin remains completely untouched underneath. It's possible to be always working at this and never actually get anywhere, the same way it's possible to be "always learning" and yet "never able to arrive at a knowledge of the truth" (2 Timothy 3:7).
This isn't just an old-fashioned mistake, either. It's exactly what happens every time someone gets caught in a sin, feels a wave of shame, and responds by gritting their teeth and white-knuckling their way through a few weeks of extra discipline — more prayer, more rule-following, more self-monitoring — until the guilt fades and the resolve quietly wears off. And then the same sin comes right back, often stronger than before. Spiritual disciplines are excellent food for a soul that's already healthy. They are not medicine for a soul that's sick. You cannot out-discipline a heart problem.
Here's why this approach can never actually work: killing sin isn't a task human effort was ever built to accomplish on its own. It requires power that only God supplies.
This is why it has to be the Spirit's work
The Spirit is specifically promised for this job. God said he would give his Spirit and take away the "heart of stone," replacing it with a heart that actually responds to him (Ezekiel 36:26, ESV; see also Ezekiel 11:19). This isn't a side effect of the Spirit's work — it's one of the things he was sent to do.
Every good thing we have comes to us through Christ, by the Spirit. Jesus said it plainly: "apart from me you can do nothing" (John 15:5, ESV). Whatever grace we have — including the ability to actually put sin to death — flows from him, and it reaches us through the Spirit he sent.
So how does the Spirit actually do this?
Three ways, generally speaking.
1. He grows things in you that crowd sin out. Paul contrasts the "works of the flesh" with the "fruit of the Spirit" (Galatians 5:19–23) and says plainly that "those who belong to Christ Jesus have crucified the flesh with its passions and desires" (Galatians 5:24, ESV). These two things — the flesh and the Spirit — can't both be flourishing in the same heart at the same time. So one of the Spirit's main strategies isn't just subtraction; it's addition. As he causes love, patience, self-control, and the rest of his fruit to grow and thrive in you, sin simply has less and less room to live.
2. He directly weakens sin at the root. This isn't only indirect. The Spirit also acts on sin's actual power directly — weakening it, wearing it down, cutting off its strength at the source, the way fire burns away whatever it touches.
3. He brings the reality of the cross into your heart by faith. He gives you genuine, felt communion with Christ in his death — not just historical facts about the cross, but something you actually experience and draw strength from. (More on exactly how that works later in this book.)
But wait — if this is the Spirit's work, why do I keep telling you to do something?
Fair question. If mortification is really the Spirit's job, why does Scripture command you to do it?
Because that's how all of the Spirit's work in us operates. "It is God who works in you, both to will and to work for his good pleasure" (Philippians 2:13, ESV) — and yet believers are still commanded, throughout Scripture, to obey, to pray, to have faith. The Spirit's work and our responsibility aren't in competition. They're two ways of describing the same reality.
The Spirit doesn't bypass you — he works through you. He engages your mind, your will, your conscience, your actual desires — not around them, and not against them. That means his help isn't a reason to sit back and wait; it's exactly what makes real effort possible and meaningful in the first place. Depending on the Spirit and actively fighting sin aren't opposites. They go together.
I want to pause here, because this distinction matters more than it might seem. I've watched plenty of sincere people spend years trapped in a specific, sad kind of misery: they know their sin is wrong, they're determined to stop, and they throw everything they have at the problem — except they're doing it disconnected from the Spirit, trying to win a spiritual battle with purely human weapons. They fight, but they never win. They're at war, but they never find peace. Sometimes they think they've finally beaten a sin, when really they've just gone numb to it for a while — they've calmed their fear and guilt down enough that the sin looks defeated, when it hasn't actually been touched at all. Then the feeling wears off, the old temptation returns exactly as strong as before, and they're right back where they started. That's a genuinely exhausting way to live — pouring everything you have into a fight you were never equipped to win alone.
And if that's the sad situation of people who are at least trying, imagine how much worse it is for someone who isn't fighting sin at all — who has simply made peace with it, and whose only real complaint is that life doesn't give them enough opportunity to indulge it.
That's exactly why this book keeps coming back to one point: this fight cannot be won by sheer willpower. It has to be fought in the Spirit's power, or it can't be won at all.
- That promised book has since been published too — it's called Communion with God. ↩