“Be killing sin, or it will be killing you.” — John Owen

One of the strange things about the Christian life is how easily we can become comfortable with the very sins that Jesus came to save us from. We know that certain things are wrong, and we may even feel guilty about them from time to time, but we learn to live with them. We make excuses, compare ourselves to people who seem worse, promise ourselves that we’ll deal with them eventually, and sometimes just assume that because we’re saved by grace, we shouldn’t be too concerned about it all.

John Owen, the great Puritan pastor and theologian, famously warned Christians to “be killing sin, or it will be killing you.” I think that’s a word the modern church desperately needs to recover, particularly in a time when we have become very good at talking about God’s love and acceptance but sometimes rather uncomfortable talking about holiness, repentance, judgment, and the seriousness of our sin.

Now, before someone misunderstands me, I believe wholeheartedly that we are saved by grace, through faith, and not by our works. The Christian life is not an endless attempt to earn God’s affection or maintain our salvation by being good enough. In fact, one of my favorite books on the subject, Walter Marshall’s The Gospel Mystery of Sanctification, argues that our growth in holiness must come from the same grace that saved us in the first place. Marshall understood that telling sinful people to try harder, without teaching them how to live out of their union with Jesus Christ, was never going to produce genuine holiness.

But understanding grace correctly should make us take sin more seriously, not less.

What Exactly Is Sin?

Most Christians have heard a preacher explain that the Greek word for sin, hamartia, means “missing the mark.” That’s a helpful starting point, but it can also leave us with a rather inadequate understanding of what we’re talking about. Missing the mark sounds almost accidental, like a basketball player missing a free throw or an archer failing to hit the bullseye.

The Hebrew Scriptures give us a much fuller picture. The word chata can communicate failing or missing the mark, while pesha describes rebellion or transgression, and avon carries the idea of iniquity, crookedness, or guilt. The biblical picture of sin includes not only failing to do what is right but actively rebelling against God and twisting what he created to be good.

I think one of our problems is that we often understand the harmfulness of sin without really understanding its evil.

We can understand why adultery is wrong because it destroys marriages, why stealing is wrong because it hurts other people, or why drunkenness and addiction are destructive because we see what they do to families and communities. But what happens when our sin doesn’t seem to hurt anybody? What happens when we think we can get away with it, or when the consequences are small enough that we’re willing to live with them?

The problem is that sin is not merely a violation of some moral code or a collection of behaviors that have unfortunate consequences. Sin is fundamentally relational. When you sin, you are sinning against the God who created you, loves you, and has brought you into his family. You are breaking the heart of your Father.

After David committed adultery with Bathsheba and arranged for her husband’s death, he prayed in Psalm 51, “Against you, you only, have I sinned and done what is evil in your sight.” Obviously David had sinned terribly against other people, but he understood that underneath those offenses was an even deeper offense against God himself.

God reveals the seriousness of sin through his law, which Paul tells us brings the knowledge of sin (Romans 3:20). The commandments reveal God’s holy character and show us how far short we fall of his righteousness. But the fullest revelation of righteousness comes not through a list of commandments, but through the person of Jesus Christ.

When we look at Jesus, we see what humanity was always supposed to be. We see perfect obedience to the Father, perfect love for neighbor, truth without cruelty, mercy without compromise, and holiness without hypocrisy. Jesus is not simply our example, of course; he is our Savior. But he also shows us what a human life completely surrendered to the Father looks like.

This is why Jesus summarized the law with the two greatest commandments: love God with all your heart, soul, and mind, and love your neighbor as yourself (Matthew 22:37–40). Sin is not merely doing bad things. It is failing to love God and other people as we ought. Sometimes that happens through obvious acts of wickedness, and sometimes through pride, selfishness, indifference, or our refusal to do the good that God has placed in front of us.

Learning to Hate Our Sin

Christians throughout history have understood that we need more than a determination to avoid the consequences of sin. We need our hearts changed so that we begin to hate what God hates and love what God loves.

The early Christians took repentance and the examination of conscience very seriously. John Chrysostom, the great fourth-century preacher, encouraged believers to examine their sins specifically rather than merely making vague admissions that they were sinners. In his thirty-first homily on Hebrews, he wrote, “For sin confessed becomes less, but not confessed worse.”

Gregory the Great, writing in his Pastoral Rule, similarly warned against the kind of repentance that grieves over sin without actually forsaking it. For Gregory, genuine repentance involved more than feeling terrible about what we had done; it meant turning away from it and seeking a different kind of life.

Over the centuries Christians have used various practices to help them in this work. Some have kept journals recording recurring temptations, sinful patterns, and areas where they need to grow. Others have practiced fasting, regular confession, and times of deliberate self-examination. These practices can become unhealthy if they lead us into constant self-condemnation, but used rightly they help us recognize what we’re otherwise very good at hiding from ourselves.

There is an old Christian sentiment that I find particularly helpful, a prayer that the sins which once seemed so sweet to us would become bitter, even like ashes in our mouths. I think that’s a wonderful thing to pray, and I think we ought to get very specific about it.

I knew a sister who struggled with meth addiction and began praying, “God, take the taste of meth out of my mouth.” And the Lord did! But then she moved on to alcohol. And isn’t that so often how sin works? We can find victory over one particular behavior while the deeper desires and patterns of our hearts remain largely unchanged. We don’t just need God to take away our appetite for one particular sin; we need him to transform the way we think, what we love, and what we desire.

That’s part of what Paul is getting at in Romans 12:2 when he tells us not to be conformed to this world, but to be transformed by the renewal of our minds. We need to learn to see sin differently. We need to pray that God would show us just how degrading it is to sit and look at pornography, reducing people made in his image to objects for our gratification. That, like Job, we would make a covenant with our eyes not to look lustfully at another person (Job 31:1). We need to recognize just how immature and self-destructive it is to tell someone off, and I don’t mean twenty minutes later when we’re feeling guilty about it. I mean while the words are still coming out of our mouths, that we would hear ourselves and think, What am I doing? This isn’t who I want to be.

Or maybe your sin doesn’t look like any of those things. Maybe you’ve inherited a pattern of worry and anxiety from your parents, and you’ve spent most of your life worrying yourself sick about things that were never really within your control in the first place. At some point, we need the Holy Spirit to help us recognize when our concern has crossed over into a refusal to trust our heavenly Father, as though the entire world rests on our shoulders rather than his.

This is what I’m talking about when I say we need to learn to hate our sin. Not to hate ourselves, and not merely to be afraid of getting caught or suffering the consequences, but to actually begin seeing these things for what they are. We want the Holy Spirit to renew our minds so that the things we once justified begin to look foolish, ugly, and completely out of place in the lives of people who belong to Jesus. We want to reach the point where we’re not merely asking God to keep us from doing the things we still secretly love, but asking him to teach us to love what he loves and hate what he hates.

Why Should Christians Fight Against Sin?

But that raises an important question: Why should we fight so hard against sin in the first place? If Jesus has already paid for our sins, if we’re saved by grace and not by works, and if our salvation rests on what Christ has accomplished rather than our own performance, why does it matter so much whether we get victory over these things?

I think this is where some Christians have a pretty shallow understanding of grace. We’ve become so concerned with making sure nobody thinks they can earn their salvation that we sometimes leave people with the impression that holiness is optional. But the New Testament certainly doesn’t talk that way. The apostles repeatedly warn believers about the dangers of sin, not because they misunderstand grace, but because they understand what sin does to us, to our relationships with others, and to our fellowship with God.

So let me give you six reasons why Christians ought to take the fight against sin seriously. Some of these are going to be pretty uncomfortable, but I think all of them are important, and all of them are rooted in Scripture.

1. Because You Might Not Actually Be Saved

I want to be 100% straightforward about this, because I think pastors sometimes avoid saying it out of fear of upsetting people. If you are deliberately living in a settled pattern of sin, with no repentance and no desire to turn from it, you may be spiritually lost. And if you are lost, then the biblical warnings about judgment and hell are not something you should dismiss.

Now, this is where we need to be both theologically careful and pastorally sensitive.

I believe in the preservation and perseverance of the saints. Salvation is a gift from God that cannot be earned, and our confidence is not in our ability to hold ourselves together but in Jesus Christ, who promises to hold on to his people. Jesus says in John 10:28 that he gives his sheep eternal life, that they will never perish, and that no one will snatch them from his hand. In John 6:39, he promises not to lose those whom the Father has given him. Paul assures the Philippians that the God who began a good work in them will bring it to completion (Philippians 1:6).

This is why the expression “once saved, always saved” is technically correct when we’re talking about someone who has genuinely been born again. However, I’ve come to believe that the expression is often pastorally unhelpful because it can give people a false sense of assurance based on something that happened years ago rather than a living faith in Jesus Christ.

I remember a mother who was absolutely convinced that her daughter was saved. Her daughter was dealing drugs, openly identified as an atheist, and had no interest in following Jesus. But her mother was confident that everything was fine because at some point years earlier, her daughter had walked down the aisle at church and prayed a prayer.

Friends, that’s not the historic Christian doctrine of the perseverance of the saints. That’s superstition. It’s treating the sinner’s prayer like some sort of magical incantation that guarantees heaven regardless of whether a person has actually come to faith in Jesus Christ.

The promise of salvation belongs to those who truly belong to Christ, and Scripture teaches that genuine faith perseveres. Jesus speaks of the one who endures to the end being saved (Matthew 24:13), and 1 John 2:19 describes those who departed from the Christian community as having demonstrated that they were never truly of them. Jesus himself warned that some people will stand before him on the day of judgment, confidently calling him Lord and pointing to their religious activity, only to hear him say, “I never knew you” (Matthew 7:21–23).

It is entirely possible to be deeply spiritually self-deluded, to think you are a Christian when in fact you are not.

This doesn’t mean that everyone struggling with sin should question whether they’re saved. In fact, I think it’s often quite the opposite. Some Christians have extraordinarily tender consciences. They hate their sin, confess it, fight against it, and yet find themselves struggling with the same temptations again and again. These are the people who need to be reminded that there is no condemnation for those who are in Christ Jesus, and that the God who began a good work in them will finish it.

John Wesley, in his sermon The Repentance of Believers, made the helpful distinction that although sin no longer reigns in the believer, it may still remain. His point was that genuine Christians continue to discover sin in their hearts and must continue to repent and believe the gospel throughout their lives.

But then there are others who never pray, have no real interest in worshiping with the church, neglect the ordinary means of grace, and live quite comfortably in deliberate disobedience to Jesus. We ought not encourage these people to presume upon their election or assure them that everything is fine because they once made a profession of faith.

The presence of a struggle against sin is not evidence that you are lost. But the comfortable absence of repentance ought to concern you.

2. Because Your Prayers Can Be Hindered

Something that seems to have been almost entirely forgotten in much of contemporary Christianity is that our behavior toward other people can affect our prayer life.

Peter tells husbands in 1 Peter 3:7 that they must live with their wives in an understanding and honoring way so that their prayers will not be hindered. Think about that for a moment. You can attend church every Sunday, know your Bible, serve in ministry, and pray for God to move powerfully in your life, but if you’re treating your wife cruelly, Peter says that your prayers can be hindered.

God made a similar point to Israel through the prophet Isaiah. In Isaiah 1:15–17, God tells his people that he will not listen to their many prayers while they continue in violence and injustice. Instead, he commands them to seek justice, correct oppression, and defend the vulnerable.

It is remarkable how often we separate our spiritual lives from the way we treat the people around us. We can think that because we had a wonderful time of worship or felt God’s presence during prayer, everything must be fine, even while we’re harboring bitterness, mistreating our families, gossiping about other Christians, or ignoring people who need our help.

I’m not suggesting that God stops loving us every time we sin, or that we somehow have to become perfect before he will hear us. But Scripture is clear that there is a real relationship between obedience and communion with God, and we should not expect to enjoy unhindered fellowship with our Father while deliberately refusing to obey him.

3. Because a Clean Conscience Should Be the Normal Experience of a Mature Christian

I think we’ve become far too accustomed to Christians living under a constant cloud of guilt and shame. We almost assume that the normal Christian experience is to struggle with the same secret sins for decades, feel terrible about them periodically, ask forgiveness, and then repeat the whole process.

But the New Testament presents us with a much better vision of the Christian life. Hebrews 9:14 tells us that the blood of Christ cleanses our consciences so that we can serve the living God, and Paul repeatedly speaks of the importance of maintaining a good conscience before God and other people.

A clean conscience doesn’t mean that we have achieved sinless perfection. It means that we are living honestly before God, confessing our sins, making things right when we wrong someone, and refusing to become comfortable with the things that God is convicting us about.

One of the things I regularly pray for myself is that God would keep me on a short leash when it comes to sin. I pray that my sinful thoughts wouldn’t become words, that my words wouldn’t become actions, and that my actions wouldn’t eventually harden into stubborn, entrenched patterns of disobedience that become increasingly difficult to uproot. I want to feel the conviction of my sin quickly and deeply, so that I might repent quickly and deeply. I’m not praying under some illusion that I’ll never struggle with sin again. Quite the opposite, actually. I’m praying that I would struggle with sin, that I would never become so comfortable with it that I stop fighting, confessing, repenting, and looking to Jesus. One of the most frightening things that can happen to a Christian is not that we feel the weight of our sin, but that we stop feeling it altogether.

There is a tremendous freedom in being able to go to bed at night without carrying the weight of something you’re trying to hide, or to come before God in prayer without deliberately avoiding the very thing he’s been confronting you about.

John C. Miller, better known to many as Jack Miller, was particularly helpful in distinguishing gospel repentance from the kind of religious penance that leaves us trapped in guilt. Miller taught that repentance is not simply something we do when we first become Christians, but an ongoing part of our lives as children of God. We bring our sin into the light, not to earn forgiveness through our misery, but because Christ has made a way for sinners to come honestly to the Father.

If your conscience is burdened today, the answer is not to hide from God or spend the next six months trying to make yourself worthy of his love. Confess your sin, receive his forgiveness, and take whatever steps of repentance are necessary. The promise of 1 John 1:9 is that if we confess our sins, God is faithful and just to forgive us and cleanse us from all unrighteousness.

4. Because You Can Grieve the Holy Spirit

Paul tells the Ephesians, “Do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption” (Ephesians 4:30).

I think this is one of the most sobering descriptions of sin in the New Testament, particularly for those of us who emphasize the presence and ministry of the Holy Spirit. We love to talk about the Spirit’s gifts, his power, and his guidance, but sometimes we forget that the Holy Spirit is not an impersonal force or some sort of spiritual electricity. He is God himself, dwelling within us, and our sin grieves him.

The theologian Sam Storms has helped me think about the distinction between grieving and quenching the Holy Spirit. Grieving the Spirit emphasizes the relational dimension of our sin, while quenching the Spirit emphasizes how we can hinder the manifestation of his presence and power. The two are certainly related, but they help us recognize that there is more than one way our sin affects our experience of the Spirit.

When Paul warns us about grieving the Spirit, the surrounding passage deals with lying, sinful anger, bitterness, slander, and the way we treat one another. These aren’t simply behaviors that God has arbitrarily decided to prohibit; they are contrary to the character of the Holy Spirit who lives within us. And just as sin can damage the intimacy of a marriage or friendship without destroying the relationship itself, our disobedience can grieve the Spirit and disrupt our enjoyment of communion with God.

Notice that Paul says this to Christians who have been sealed by the Spirit for the day of redemption. Their security in Christ doesn’t make their sin inconsequential. Quite the opposite. Because we belong to God and his Spirit dwells within us, we should take seriously the things that grieve him.

5. Because You Can Quench the Holy Spirit

Paul also warns the Thessalonians, “Do not quench the Spirit” (1 Thessalonians 5:19). The language here is different. To quench something is to extinguish or suppress a fire, and the picture Paul gives us is of Christians somehow hindering the work of the Holy Spirit.

Sam Storms has written extensively about this, particularly in his article Do Not Quench the Spirit! He points out that while the Holy Spirit is sovereign and omnipotent, Scripture nevertheless teaches that Christians can resist, suppress, and hinder what he desires to do in and through the church. This is especially clear in the immediate context of 1 Thessalonians 5, where Paul tells believers not to despise prophecies, but to test everything and hold fast to what is good.

I find this particularly important for Christians who believe in the continuing gifts and miraculous ministry of the Holy Spirit. We can become so concerned with maintaining control, avoiding anything uncomfortable, or protecting ourselves from the possibility of mistakes that we end up resisting the very work of God we’ve been praying to experience. Of course, everything must be tested against Scripture, and discernment is not the enemy of the Spirit. But neither should our fear or our theology become an excuse for suppressing what God may be doing.

And this isn’t only about prophecy, healing, or spiritual gifts. Storms also points out that we can quench the Spirit by relying on our own strength rather than his power, by refusing his leading, or by trying to carry out ministry without dependence upon him.

There is something deeply contradictory about asking God to move powerfully in our churches while deliberately resisting his work in our own hearts. We want the Spirit’s power, but are we willing to surrender to his holiness? We want him to speak, but are we willing to listen and obey?

Sin can rob us of intimacy with the Holy Spirit, and it can hinder our experience of his power. Neither is something Christians should treat lightly.

Can I be really straightforward here? Dude, when I pray, I WANT power. I want to see things happen! I want to see people healed, people delivered, lives transformed, and the gifts of the Holy Spirit operating in the church. Don’t you? I don’t want to spend my life talking about the things God used to do, or even just the things he might theoretically do today. I want to see him at work among us. But what if the habitual sin you’re making excuses for, the bitterness you’re nursing, the secret compromises you’re hiding, or the areas of your life where you’re refusing to obey the Lord are actually hindering your experience of the very power and gifts you’ve been praying for? What if we’re asking God to pour out his Spirit while simultaneously quenching what he’s already doing? Now, I’m not saying that every unanswered prayer or absence of miraculous gifts is the result of someone’s personal sin. Scripture doesn’t allow us to make that assumption. But surely we ought to ask ourselves whether we’re resisting the very Spirit whose power we so desperately want to experience.

6. Because Sin Robs You of the Joy of Your Salvation

After David’s terrible sin, he prayed in Psalm 51:12, “Restore to me the joy of your salvation.” David understood something that every Christian who has spent time wandering in sin eventually discovers: sin has a way of robbing us of the very joy that God intends us to experience in our relationship with him.

There’s a particularly miserable place that Christians can find themselves in when they’re trying to hold on to Jesus and their sin at the same time. They can’t really enjoy the world or their sin the way they once did because the Holy Spirit continues to convict them, but they’re also not enjoying the peace, freedom, and fellowship with God that come from walking in obedience.

They end up stuck somewhere in the middle, feeling too guilty to really enjoy their sin but too attached to it to enjoy the things of God.

Now, we should be careful here. Not every season of spiritual dryness, sadness, or discouragement is the result of some hidden sin. Christians can experience depression, grief, exhaustion, and deep suffering even while faithfully following Jesus. We shouldn’t automatically assume that someone who has lost their joy must be living in disobedience.

But sometimes the explanation really is that simple. We are holding on to something that God has been calling us to surrender, and the longer we hold on to it, the more miserable we become.

The Christian life was never intended to be an exercise in seeing how much sin we can get away with while still making it into heaven. Jesus came so that we might have life, and have it abundantly (John 10:10). While that certainly doesn’t mean a life free from suffering, it does mean that the freedom, peace, and joy of knowing God are far better than anything our sin has to offer.

Be Killing Sin, but Don’t Forget the Gospel

I want to finish with something important, because I know that an article like this can land very differently depending on who is reading it.

For some of you, this might be exactly the warning you need. You’ve become comfortable with things that you know are wrong, you’ve ignored the conviction of the Holy Spirit, and you’ve been presuming upon God’s grace rather than responding to it with repentance. If that’s you, I hope you’ll take the warning seriously and turn back to Jesus.

But for others, particularly those with tender consciences who already feel overwhelmed by their failures, I don’t want you to come away thinking that the solution is simply to try harder or that God is perpetually disappointed with you.

Walter Marshall understood something that Christians often forget: the power to live a holy life doesn’t originate in our own determination. It comes through our union with Jesus Christ. In The Gospel Mystery of Sanctification, he teaches that holiness, like justification, is a gift of grace, received through faith and worked out in our lives by the Holy Spirit.

That’s not an excuse for laziness or passivity. Paul tells us in Romans 8:13 that if by the Spirit we put to death the deeds of the body, we will live. We’re commanded to put sin to death, but notice that we’re commanded to do it by the Spirit.

John Owen was right that we must be killing sin or it will be killing us, but we should also remember that we’re not being sent into that battle empty-handed.

God has not left us alone.

And that brings me to something I’d like to explore in a future article, because knowing that we should fight sin and actually knowing how to overcome it are two very different things.

In the next post, I want to talk about how Christians can actually grow in victory over sin, not through guilt, fear, willpower, or some complicated spiritual formula, but through the resources God has already provided for us.

He has given us the gospel, which continually reminds us of who we are in Jesus Christ and what he has accomplished for us. He has given us the Holy Spirit, who changes our hearts, strengthens us in weakness, and empowers us to put sin to death. And he has given us the people of God, the Church, where we are encouraged, corrected, prayed for, held accountable, and strengthened through the ordinary means of grace.

These are not three unrelated strategies for becoming better Christians. They are gifts from a Father who is committed to finishing the work he began in his children.

So yes, be killing sin, or it will be killing you. But don’t forget that the God who calls you to holiness is the same God who has promised to make you holy, and he has not left you to figure it out on your own.

Up Next: How Do We Actually Overcome Sin? The Gospel, the Holy Spirit, and the People of God.