What does it mean to mortify sin?
Question 06060
John Owen’s seventeenth-century treatise on mortification of sin remains one of the most searching pieces of practical theology in the English language. But the concept did not originate with Owen. It is rooted in the apostle Paul’s instruction to “put to death therefore what is earthly in you” (Colossians 3:5), and it names something every believer must understand if they are to grow in genuine holiness. So what does mortification actually mean, and how does it work?
The Meaning of the Term
Mortification comes from the Latin mortificare, meaning to put to death. In theological usage it refers to the deliberate, ongoing work of weakening and subduing sinful desires, patterns, and tendencies in the life of the believer. Paul uses the Greek word nekrōsate in Colossians 3:5, an aorist imperative that carries real urgency: “Put to death, therefore, what is earthly in you: sexual immorality, impurity, passion, evil desire, and covetousness, which is idolatry.” The language is vivid and intentional. He is not describing something that happens automatically or gradually without engagement. He is commanding action.
The same thought appears in Romans 8:13: “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.” The connection between mortification and life is direct. Paul is not suggesting that the believer earns salvation through efforts at holiness. He is saying that genuine spiritual life expresses itself in a willingness to deal seriously with sin. A person who makes no effort to resist sin gives little evidence that the Spirit of God dwells in them at all.
What Mortification Is Not
A number of misunderstandings have attached themselves to this concept and need to be cleared away. Mortification is not the eradication of sinful desire. The Scriptures nowhere promise that the war against the flesh will end before glorification. Romans 7 describes an ongoing conflict, and Paul’s instruction in Galatians 5:16 to “walk by the Spirit and you will not gratify the desires of the flesh” assumes that those desires remain present and must be actively resisted. The goal of mortification is not the elimination of temptation but the weakening of sin’s power over the will.
Mortification is also not asceticism. Some Christian traditions have practised physical self-denial as a means of subduing sinful impulses. While fasting has genuine biblical warrant, the idea that the body itself is the problem to be punished misreads the biblical picture. Paul warned the Colossians that rules about “do not handle, do not taste, do not touch” and harsh treatment of the body are of “no value in stopping the indulgence of the flesh” (Colossians 2:21-23). The problem is not the body but the heart, and physical self-denial without spiritual engagement is simply discipline, not mortification.
The Role of the Holy Spirit
Romans 8:13 is careful to specify that believers put to death the deeds of the body “by the Spirit.” Mortification is not self-improvement by spiritual determination. It is cooperation with the Holy Spirit’s sanctifying work. The Spirit provides the power; the believer provides the willingness and the effort. Owen’s famous formulation captures this: we must be killing sin, or sin will be killing us. But this killing is not done in our own strength alone, and any approach to mortification that forgets the Spirit’s agency will collapse under the weight of its own effort.
This has important pastoral implications. A believer who struggles seriously with sin and wants to be free of it is not in the same position as a believer who has made peace with sin and ceased to care. The presence of genuine conflict, the experience of grief over sin, and the desire to be free are all evidences of the Spirit’s work. The mortification process involves honest confession, the renewing of the mind through Scripture (Romans 12:2), sustained prayer, and the practical step of removing occasions for sin where possible.
The Positive Dimension
Mortification in Paul is always paired with what theologians sometimes call vivification — the putting on of the new self. Colossians 3 does not stop at “put to death”; it continues with “put on then, as God’s chosen ones, holy and beloved, compassionate hearts, kindness, humility, meekness, and patience” (Colossians 3:12). Genuine mortification of sin creates space that must be filled with the positive fruit of the Spirit. A person who merely suppresses sinful behaviour without cultivating godly character will find the suppression progressively harder. The negative and positive dimensions of sanctification belong together in the same passage for good reason.
So, now what?
Mortification is not an optional extra for particularly serious Christians. It is the ordinary work of every believer in the normal Christian life. The question is not whether a Christian should engage in it but whether they are doing so honestly and with genuine reliance on the Spirit’s help. If there is a pattern of sin that has been left unaddressed, the starting point is honest confession and a genuine desire for change, followed by the practical steps of renewing the mind, removing the occasions of temptation, and asking the Spirit for power to resist. The war will continue until glory, but it is a war that can be fought and, by grace, progressively won.
“If by the Spirit you put to death the deeds of the body, you will live.” Romans 8:13