And to get a grasp of what it means to kill sin, let's talk about—you guessed it—what killing sin doesn't mean…
1. Killing sin does NOT mean sinless perfection.
So when we set ourselves upon killing sin in our lives, we must not get discouraged if we haven't reached perfection yet. In fact, none of us will in this lifetime.
God has ordained that your life be one of mortification. Don't be bitter at God for this. He receives glory through the process of making you more holy. For encouragement in this work, read all of Romans 8, which talks about how we groan, waiting eagerly for the completion of our redemption, and how the Holy Spirit helps us in our weakness, and about God's promise that He will finish what He began.
2. Killing sin does NOT mean disguising or hiding sin.
Other times, we may not simply hide our sin; we may disguise our sin as righteousness. We may justify sinful relationships by passing them off as "evangelistic" opportunities. We may do hermeneutical gymnastics to explain why our homosexual perversion actually brings glory to God. We may foolishly bless our worldly pursuits by convincing ourselves and others that God's highest aim is to make us happy. Don't fall into these traps. Here's Owen to help snap us out of our prevarication:
When you in some outward way stop the practice of any sin, others may look at you as a changed man or a changed woman. But God knows that to your former sin you've added wicked hypocrisy, and you're now on a safer path to hell than you were before. You've got a different heart than you had, but one that is more deceitful; not a new heart, that is more holy. (I updated the language a bit to make it more readable.)
3. Killing sin does not mean being a "nice" person.
You must mortify your sin. And if your sin is naturally more internal and less visible, it is in many ways more dangerous to your soul:
The sins of some men are quite evident, going before them to judgment; for others, their sins follow after. (1 Timothy 5:24)
When I kept silent about my sin, my body wasted away
Through my groaning all day long.
For day and night Your hand was heavy upon me;
My vitality was drained away as with the fever heat of summer.
4. Killing sin does NOT mean occasional victory over sin.
Remember the culture we've created of spiritual highs at youth retreats and Christian rock concerts. We get all excited, and that emotional excitement motivates us for a week or so to something that looks like obedience but quickly fades. This Christian culture has bred a wrong view of the fight against sin. We think it's just an occasional thing we have to engage in; but then, just when we think it's dead and defeated, it comes back!
This same thing happens on a grand scale whenever there's some great calamity or judgment in the world. Remember 9/11? People flooded into churches, seeking God's mercy and help. An awareness of judgment came near and people made a big show of repentance and despair, but it was only fleeting. The churches soon returned to their normal attendance.
Like Pharaoh, repeatedly repenting and then unrepenting, people make vows to God in times of great distress or trouble. "God, if you get me out of this, I promise I'll never ________!" What's wrong with this? It shows that you think God owes you something if you do certain things. When we think like this, it shows that we think we can jack God around as if He were a fairy godmother or a genie (who wants us to just follow our heart).
A terrible experience or some painful consequences of sin may cause you to resolve never to return to it, but be honest—when it comes to sin, your memory is pretty short-lived. Your sinful flesh is happy to respond to your fiery but temporary backlashes by pretending to be dead…until you let your guard down…again.
But true mortification, true victory over sin, is demonstrated by long-term obedience and bearing of fruit. We are not to be rocky soil which responds to the Word of God with fleeting joy but then is scorched and burned out by the sun, by the difficulty of the fight, by worldly concerns. We want long-term, steady, persevering obedience from the Christian. It's fun to have an amazing conversion story, or some heroic spiritual struggle you can tell people about, but Jesus says "it is the one who has endured to the end who will be saved" (Matthew 10:22). Which is to say, it's not those with the most impressive stories, but those who persevere in faithfulness till they die, who will enter into eternal life.
What does it mean?
1. Killing sin is a habitual weakening of sin.
From the day of our birth, we begin to form sinful habits. We get into patterns of sinning. We become so entrenched in these habits that we are unable to escape by our own power. We need the power of the Holy Spirit to exert a greater force than the force of sin. And this is one way that sin is put to death in our lives with the help of the Spirit: sinful habits are weakened.
The best picture we have of this reality is from the reality of Christ's crucifixion, which is used to describe the excruciating death of our sin:
As a man nailed to the cross he first struggles and strives and cries out with great strength and might, but, as his blood and spirits waste, his strivings are faint and seldom, his cries low and hoarse, scarce to be heard; when a man first sets on a lust or distemper, to deal with it, it struggles with great violence to break loose; it cries with earnestness and impatience to be satisfied and relieved; but when by mortification the blood and spirits of it are let out, it moves seldom and faintly, cries sparingly, and is scarce heard in the heart; it may have sometimes a dying pang, that makes an appearance of great vigor and strength, but it is quickly over, especially if it be kept from considerable success. (Owen, Mortification of Sin)
The Holy Spirit puts sin to death in us by weakening its habit.
Have patience in this work—lasting victory over sin takes time. Some people are granted immediate miraculous victory over some great sin or temptation. But more often, we must habitually weaken the acting of sin in our hearts. When we first become aware of some sin in our lives and set ourselves to repentance, the normal thing to happen is that it takes time and discipline to have lasting victory over that sin. And we must grow towards more regular and consistent victory. Again, this is the normal life of a Christian—fighting against sin.
2. Killing sin is constant fighting against it.
If I expect that my toddlers will be perfectly obedient and intelligent and act like mature adults, I only ever end up disappointed. It causes me to resent the work of discipline every single time I have to do it. But, if I expect my children to be rebellious sinners, as God tells me to, I have the joy of engaging in the work of teaching and training them in righteousness. Rather than seeing the work as a burden, I can freely give myself to it in hope that God will use my efforts to produce fruit.
A couple months ago, my wife, Dani, and I watched through the Band of Brothers series. Watch this scene:
When we expect to have to fight against sin, and accept that that's the life Jesus has called us to, we can walk in joy and freedom and victory. But if you're constantly resenting the Lord for calling you to a life of fighting sin, you will not produce fruit. You must be convinced of the need to kill sin in order to effectively destroy it. If you're not convinced your enemy is really an enemy, you will never wholeheartedly commit yourself to destroying it.
One of the clearest ways you can assess if someone truly sees their sin as a mortal enemy is in their response to rebuke and correction. Do they seek to justify themselves? Do they always have an explanation for their sin? Do they minimize their sin? Or, do they own up to it and take responsibility, confessing their sin and repenting?
Band of Brothers was so helpful in giving me context for understanding the life-and-death nature of war and how it applies to our spiritual lives. For one thing, correction and rebuke are so necessary in the context of battle. You don't get offended when your commanding officer tells you you did something wrong, because you probably endangered people's lives by doing it. You don't resent it when your CO tells you to pay better attention, to cease fire, or to change your socks. Your life, the lives of your fellow soldiers, and the completion of your mission depend on your willingness to be corrected.
3. Killing sin means frequent success!
Because of this, true mortification—true killing of sin—consists in regular victories over sin. If you are really fighting, you will be able to identify ways that you’ve overcome sin and temptation in your life.
One way this happens is through the development of godly habits. This is the positive side of what we said earlier, that sinful habits must be weakened. As sinful habits are weakened by the power of the Spirit, we must labor to replace them with godly habits.
It's not enough to just get rid of the sinful desires and habits. You must plead with the Holy Spirit to grow desires for holiness and godliness and righteousness inside you, and to put to death wicked desires. But then you must apply yourself to creating space for the Spirit of God to work. You must discipline and commit yourself to godly habits.
One such godly habit is the reading of Scripture. I've been a Christian since about 2000. Sadly, 2014 was the first time I ever successfully completed a one-year Bible reading plan. I had many false starts and many half-successes, but I've finally begun to develop a habit of reading Scripture. Several of the men here and I are currently doing the M'Cheyne Bible reading plan, which involves reading the entire Bible in a year, plus the New Testament and the Psalms a second time. Sure, it's checking off a box, but it's also discipline. In fact, it's become such a part of my daily routine, that at times where I would have habitually gotten out my phone to check Facebook or play an inane iPhone game, I get out my phone to read a chapter of Scripture. Call the Bible reading plan a legalistic work of box-checking, but I've seen it begin to develop righteous habits in the place of wicked worldly habits. And the more we read Scripture—even when it doesn't seem to stick—the more our thinking becomes shaped by the truth in God's Word.
When we by faith apply ourselves to self-discipline in spiritual matters, the Spirit will work. We must join with the Spirit in fighting against sin. We must employ every means provided to us to develop godly habits.
Think about how you can develop habits of prayer, service, worship, fellowship, and study. Habits, habits, habits!
I'll leave you with a helpful quote from Licensed to Kill by Brian Hedges:
Mortifying sin is like weeding a garden. Left to itself, a garden will become overgrown with weeds, choking out the good plants. Likewise, a person who doesn't put sin to death finds his heart so overgrown with sin that the comfort and joy of walking with Christ is choked out. But there is more to growing a healthy garden than weeding it. Good seeds must be planted, watered, and fertilized! Then God must give the growth. So it is in a life of holiness: we must weed out sin and cultivate the graces of the Spirit in our lives.
…we can kill sin only when we cultivate the virtues of Christ and the graces of the Spirit in sin's place. And the only way to cultivate this kind of character is through the regular practices of Christian community: peacemaking, Scripture intake, admonishing one another, worship, and grateful prayer. These are the practices that help us set our affections on Christ and put our mouths out of taste for the deadly pleasures of sin by giving us greater satisfaction in him.