“So then, brothers, we are debtors, not to the flesh, to live according to the flesh. 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. For all who are led by the Spirit of God are sons of God.” (Romans 8:12-14)
The article title reads, “Meet Wally the Emotional Support Alligator.” Yes, an emotional support alligator. The story explains that a Pennsylvania man lives with two alligators, one of whom is a registered emotional support animal named Wally. Wally follows him around the house, enjoys being petted, makes nests out of blankets, and even lounges on the couch and bed. The owner insists Wally has never bitten anyone, while also warning that alligators do not make good house pets because they are still wild animals.
Most of us read something like that and think, This is insane. Why? Because no matter how “domesticated” the alligator appears, no matter how calm it seems today, we know what it is. It is a dangerous creature. It may look safe, but it is not safe. You do not cuddle what can kill you.
And yet many Christians treat something far more lethal with far more familiarity. Not an alligator in the living room, but sin in the heart.
Romans 8 is one of the clearest chapters in Scripture on the believer’s assurance. It begins with “no condemnation” (Romans 8:1) and climaxes with “no separation” (Romans 8:39). But in the middle of this chapter of comfort, Paul speaks with startling severity:
“So then, brothers, we are debtors, not to the flesh, to live according to the flesh. 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 8:12–13)
The danger is not that Christians are imperfect. The danger is that many professing Christians grow comfortable with indwelling sin. We tolerate it, negotiate with it, excuse it, and keep it close, as if we can domesticate what is by nature hostile to God and destructive to us.
Paul will not allow a peacetime mentality toward sin. The Christian life is war. Not war to earn justification, but war because justification has brought a new allegiance, a new identity, and a new power: the Holy Spirit.
Paul’s logic is blunt: either sin dies or you do. The Puritan John Owen said it like this: “be killing sin or sin will be killing you.”
“If you live according to the flesh you will die.” (Romans 8:13) That “death” is not mere physical death. Everyone dies physically. Paul is warning about spiritual and eternal death, the judgment that belongs to those who remain “in the flesh,” meaning unregenerate and outside Christ.
But Paul is addressing “brothers,” and that raises a tension. How can a chapter about security include a threat like this?
Here is the theological clarity: Paul is not teaching that true Christians can lose salvation. He is teaching that the absence of “mortification” (an old Puritan term for putting sin to death in your life) reveals the absence of the Spirit. Verse 14 explains verse 13:
“[For] all who are led by the Spirit of God are sons of God.” (Romans 8:14)
What does it mean to be “led by the Spirit” here? Not mainly guidance about everyday decisions, or which job to choose and hose to buy, but the Spirit’s active leadership into pursuing holiness. In context, the Spirit leads the believer to put sin to death. Mortification is not the basis of our sonship, but it is the evidence of it. No mortification, no Spirit. No Spirit, no sonship.
So why kill sin?
First, because eternity is at stake. A life that makes peace with sin, that settles under sin’s controlling influence without repentance or fight, is a life without the Spirit moving away from the kingdom of God. The trajectory of your life matters. Not sinless perfection, but direction. Are you moving toward God in repentance and obedience, or drifting toward sin with increasing comfort?
Second, because sin destroys life and joy now. Sin is not only guilty, it is corrosive. It damages marriages, friendships, churches, and consciences.
John Owen famously said, “[Sin] is a cloud, a think cloud that spreads itself over the face of the soul, and intercepts the beams of God’s love and favor. It takes away all sense of the privilege of our adoption; and if the soul begins to gather up thoughts of consolation, sin quickly scatters them.”
Sin is a cloud that blocks the warmth of God’s love. The love is real, but our enjoyment of it is hindered when sin is cherished. Peter calls sinful passions “waging war against your soul” (1 Peter 2:11). They are not neutral habits. They are hostile forces at war against you.
This is why repentance is often connected with “times of refreshing” from the presence of the Lord (Acts 3:19). For some, persistent spiritual heaviness and depression may be the result of unrepentant sin in your life. That is not to deny physiological complexity, but to insist that the heart must not be ignored.
Killing sin does not mean reaching perfection. Scripture is clear that the believer has an ongoing internal conflict: “the desires of the flesh are against the Spirit” (Galatians 5:17). The fight remains until death. In fact, a lack of struggle is often more concerning than the struggle itself, because if there is no struggle, then there is no indwelling Holy Spirit.
Killing sin also does not mean merely managing external behavior while indulging internal desires. If lust is merely relocated from the computuer screen to the imagination, nothing has been mortified.
Nor is killing sin only about isolated “big sins.” Mortification is about severing sin at the root. It is not “whack-a-mole” behavior management. It is warfare against the desires that give birth to sinful thoughts and deeds.
Paul’s phrase is vivid: “put to death the deeds of the body” (Romans 8:13). This is execution language.
Paul says in Colossians 3:5-6, “Put to death therefore what is earhtly in you: sexual immorality, impurity, passion, evil desire, and covetousness, which is idolary. Notice, those are all internal desires. Its not just about external actions, but internal desires.
Jesus said in Matthew 5:29-30, that if your right eye causes you to sin, gouge it out. If your right hand causes you to sin, cut it off. Why? It’s better to lose a member of your body than the whole body be thrown into hell.
John Owen called it “draining sin’s lifeblood.” And so, the goal is to choke out sin’s power and presence from your life.
Paul gives the controlling method in one phrase: “by the Spirit.” (Romans 8:13)
Mortification is neither self-salvation nor spiritual passivity. It is Spirit-empowered exertion. You fight, and you fight in dependence on the indwelling Holy Spirit.
Here are practical paths from the Scripture and from John Owen’s book, The Mortification of Sin :
Underneath it all is this: killing sin is a fight for superior joy. Sin promises pleasure, relief, control, escape. The gospel offers something better: Christ Himself. Owen and others were right to say that sin shrivels when the cross stays in view. Not because guilt alone transforms us, but because the cross shows both the horror of sin and the beauty of the Savior.
So do not cuddle with a wild alligator. Do not domesticate what must be killed in your life. By the Spirit, put it to death. And as you do, you will find that the Spirit who leads you into war also leads you into life.
