In 1656 Puritan Pastor John Owen felt concerned that professing Christians were too “at peace in the world” (vii). He also believed that much of the teaching against sin in his day produced “superstition, self-righteousness and anxiety of conscience” in the hearers (viii). So, Owen wrote a little book called The Mortification (or “Putting to Death”) of Sin in Believers based on the second half of 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.” 

This verse outlines the duty of all believers, those who are “not in the flesh but in the Spirit” (v. 9). God encourages believers in their fight against sin. If we properly fight against sin we shall live. The means of mortification results in abundant life. But lest we become confident in our own strength we must know this, “It is a work of the Spirit, and it is by Him alone that we are to experience victory” (3). The Spirit empowers us to fight against indwelling sin in the same way that Christ crucified our former way of life in the cross (Rom. 6:6). As we put to death our sinful nature, our joy, comfort, and vigor increasingly come to life.

Principles of Mortification

Mortification is the duty of all believers (Col. 3:5; 2)

For six reasons, every believer must “Always being killing sin or it will be killing you” (5). First, believers will only be perfected in glory (Phil 3:12). We can only rest when sin is dead. Second, sin always works to produce bad fruit. “He that stands still and allows his enemies to exert double blows upon him without resistance will undoubtedly be conquered in the end” (7). Third, unchallenged sin becomes stronger and more deceitful. “Sin, if not continually mortified, will bring forth great, cursed, scandalous, and soul-destroying sins (Gal 5:19-20)” (Page Number??) Fourth, God gives us the Holy Spirit and our new nature to oppose sin and lust (Gal. 5:17; 2 Pet. 1:4). We must not neglect his gifts. Fifth, believers grow weaker toward God as sin strengthens in them. Unexercised grace will languish. Sixth, our spiritual growth is our daily duty (2 Pet. 3:18). “He who does not kill sin along the way is making no progress in his [Godward] journey” (10).

Those who do not put sin to death do themselves and others great harm. They promote a form of godliness that has no power to acquire eternal life.

Mortification Is by the Spirit

Any merely outward attempt to kill sin—taking vows, imposing strict rules on our bodies (Col. 2:23), adhering to religious duties—will fail. If God has not promised to work through these means they are powerless. If we put confidence in our efforts, even in our prayers, self-discipline, and promises, we sidestep the power of the gospel.

Mortification is accomplished by the Spirit. The Holy Spirit gives us all the blessings we have in Christ including sanctification. God gives his Spirit to conquer our sin.

The Spirit mortifies our sin in a variety of ways. The Spirit causes us to abound in grace so that his fruit restricts the fruits of the flesh. The Spirit destroys our lusts. “He is the fire that burns up the very root of lust” (18). The Spirit causes believers to commune by faith with Christ in his death and sufferings. Without the Spirit’s help we would fight against sin but with no strength for the battle.

Even though the Spirit must put sin to death we are responsible for doing it with the Spirit’s help.

Mortification Is of Great Benefit

To live a joyful spiritual life we must kill sin. Mortification of sin does not guarantees a pleasant life, as Psalm 88 makes plain. But without mortification our spirits cannot thrive. Failing to put sin to death will weaken the soul, and deprive it of its vigor. David complained of being unsound, feeble, and crushed by sins he let live (Ps. 38, 40, 51, etc.). “Sin untunes…the heart itself, by entangling its affections” (23). The soul that is entangled with worldly pursuits cannot be full of God. “Sin will also darken the soul, and deprive it of its comfort and peace” (24). Sin is like a cloud that intercepts “all the beams of God’s love…” (24). Unmortified hearts are like fields so overgrown with weeds that no good crop can grow.

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