Mortification is the ongoing, Spirit-enabled work of killing sin in the believer's life — not managing it, not negotiating with it, but actively putting it to death. Paul commands it in Romans 8:13: "If by the Spirit you put to death the deeds of the body, you will live." And in Colossians 3:5: "Put to death therefore what is earthly in you." The key phrase is "by the Spirit" — mortification is not self-effort or asceticism; it is a Spirit-empowered act in which the believer actively opposes sin using the means God provides: the Word, prayer, fellowship, fasting. John Owen's famous line summarizes it: "Be killing sin or it will be killing you." The indicative grounds the imperative: we mortify sin because we have already died to it in Christ (Rom 6:6) — but that death must be worked out in practice. Mortification is the evidence that sanctification is real.
MORTIFICATION, n. The act of mortifying or subduing the passions and appetites by penance, abstinence, or painful severities inflicted on the body. We tame the body by mortification. 2. The subduing of the passions, sensual desires and affections; the exercise of piety and abstinence, with a view to subdue the lusts of the flesh. 3. Humiliation of pride; depression of vanity. 4. In surgery, the loss of vitality in some part of a living animal.
MORTIFY, v.t. To destroy the organic texture and vital functions of some part of a living animal; to cause to die. 2. To subdue; to abase; to reduce; to humble; as, to mortify the appetites or passions. 3. To humble; to depress; to abase. The news was enough to mortify a saint.
• Romans 8:13 — "If by the Spirit you put to death the deeds of the body, you will live."
• Colossians 3:5 — "Put to death therefore what is earthly in you: sexual immorality, impurity, passion, evil desire, and covetousness, which is idolatry."
• Romans 6:11–12 — "Consider yourselves dead to sin and alive to God in Christ Jesus. Let not sin therefore reign in your mortal body."
• Galatians 5:24 — "Those who belong to Christ Jesus have crucified the flesh with its passions and desires."
• Matthew 5:29 — "If your right eye causes you to sin, tear it out and throw it away. It is better that you lose one of your members than that your whole body be thrown into hell."
Latin:
mors / mortis (death) + facere (to make/do)
→ mortificare = to cause death, kill
→ mortification = the act of killing/putting to death
Greek NT terms:
θανατόω (thanatoō, G2289) — to put to death; used in Rom 8:13
"put to death (thanatoō) the deeds of the body"
νεκρόω (nekroō, G3499) — to make dead, reckon dead
(Col 3:5 in some manuscripts; Rom 4:19)
νεκρός (nekros, G3498) — dead; "reckon yourselves dead to sin"
(Rom 6:11)
The concept vs. mere asceticism:
Asceticism = bodily discipline as a means of earning favor
Mortification = Spirit-empowered opposition to sin because
of union with Christ's death; the motive is worship,
not merit; the power is the Spirit, not willpower
Modern Christianity has largely abandoned the language and practice of mortification. It has been replaced with "managing triggers," "healthy coping mechanisms," and the language of addiction recovery — which, while useful, focuses on behavior modification rather than the death of sin's root. Even more damaging is the idea that grace makes mortification unnecessary — that "resting in Christ" is the whole of the Christian life. But rest and war are not opposed; the Christian rests in Christ while warring against flesh. The man who never fights his sin has not met the grace that teaches us to "deny ungodliness and worldly lusts" (Titus 2:12). Grace does not abolish the imperative — it empowers it.