Be Killing Sin: The Doctrine of Mortification

North Creek Baptist

14 September 2025

Title: Be Killing Sin:

“Be Killing Sin: The Doctrine of Mortification”

Romans 8:13

Introduction:

Illustration: A garden overrun with weeds. Left alone, weeds choke life. You don’t negotiate with weeds—you uproot them. So it is with sin.

Set the stage: Many Christians want comfort without the cross, forgiveness without fighting sin, but Paul says: “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.”

Main thought: Mortification is not optional; it is the Spirit-empowered, ongoing work of killing sin so that we might live to God.

I. The Necessity of Mortification

Text: Romans 8:13a – “If you live according to the flesh, you will die.”

The seriousness of sin: Sin is not a trifle—it is treason against a holy God.

The consequence of living in the flesh: eternal death, separation from God.

Supporting Scripture: Colossians 3:5 – “Put to death what is earthly in you…”

Pastoral Interjection: A believer cannot coddle sin. To tolerate it is to make peace with the enemy that seeks your soul.

II. The Power for Mortification

Text: Romans 8:13b – “But if by the Spirit you put to death the deeds of the body, you will live.”

Mortification is not self-reform, moralism, or legalism.

It is Spirit-enabled: “By the Spirit…” The Spirit applies Christ’s death to the believer’s daily life.

Supporting Scripture: Galatians 5:16 – “Walk by the Spirit, and you will not gratify the desires of the flesh.”

Pastoral Interjection: Willpower may restrain sin for a season, but only the Spirit can slay it.

III. The Practice of Mortification

Text: “…you put to death the deeds of the body…”

Active command: mortification requires intentional effort, not passivity.

Practical means:

The Word of God (Hebrews 4:12 – exposes and convicts).

Prayer (Matthew 6:13 – “Deliver us from evil”).

Faith in the gospel (Romans 6:11 – “consider yourselves dead to sin and alive to God”).

Sacramental grace – Baptism reminds us we died with Christ; the Lord’s Supper nourishes us with Christ’s death and resurrection.

Accountability and fellowship (Hebrews 3:13 – exhort one another daily).

Supporting Scripture: Colossians 3:10 – “…put on the new self, which is being renewed in knowledge after the image of its creator.”

Illustration: John Owen’s maxim—“Be killing sin, or sin will be killing you.

IV. The Fruit of Mortification

Text: “…you will live.”

Not only eternal life but a foretaste of it now.

Mortification does not make life miserable; it frees us to live in joy, holiness, and communion with Christ.

Supporting Scripture: Galatians 2:20 – “I have been crucified with Christ. It is no longer I who live, but Christ who lives in me.”

Pastoral Interjection: True happiness is not found in indulging sin, but in being free from it.

Conclusion

I is not a burden but a blessing. The Spirit empowers us not only to resist sin but to walk in resurrection life.

Re-emphasize: Those who live in the flesh die, but those who, by the Spirit, put sin to death will live.

Illustration: A soldier cannot make peace with an enemy bent on destruction. You either fight, or you perish.

Invitation

To unbelievers: You cannot mortify sin apart from Christ. Come to Him who died and rose again. He alone breaks sin’s dominion.

To believers: Are there sins you’ve tolerated? Lay them down. Ask the Spirit to empower you in the battle. Seek the joy of freedom.