Defeat Lust & Pornography Mortification of Sin Commentary
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The Mortification of Sin (Part 2 of 15)

Last Updated: April 2, 2024

Last week we began our look at Of the Mortification of Sin in Believers, John Owen’s classic work on killing sin. This book has been a help to many Christians in the last 300 years in the fight against temptation.

The 19th century Scottish minister John Duncan rightly said, if you are going to read this book you will need to “prepare yourself for the knife.”

In the first chapter of Owen’s work, he establishes the biblical foundation for the task of killing sin: “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 8:13). He spends his first chapter explaining what this verse means.

Romans 8:13 – Mortifying the Deeds of the Body

1. True mortification is the condition of eternal life.

Notice the key words “but if.” If you put to death the deeds of the body, then you will live. Owen explains this is not, strictly speaking, a cause-and-effect relationship. Eternal life is the free gift of God (Romans 3:23), not something we cause to happen. Rather, mortification is the divinely appointed means, and eternal life is the end. When God gives the gift of eternal life, he also plants within the believer the drive and power to continually slay sin throughout his or her life.

For Owen, this condition supplies readers with the main motive to mortify sin: we put to death the deeds of the body because we know there is a necessary connection between killing sin and experiencing fullness of life, both in this age and the age to come.

2. True believers have the duty to mortify sin.

Who is the “you” to whom this command is addressed? It is the same “you” to whom there is “no condemnation” (v.1), those who are “not in the flesh but in the Spirit” (v.9), and those who are indwelt by “the Spirit of him who raised Jesus from the dead” (v.11).

Only believers can mortify sin. Only those who are freed from the “condemning power of sin,” as Owen puts it, can put the “indwelling power of sin” to death. To expect those who are not Christians to mortify sin only teaches self-righteousness.

3. The true cause of mortification is the Holy Spirit.

We mortify sin “by the Spirit.” While we perform the duty of mortification, the Spirit is the one who empowers it. We do not kill sin by sheer willpower, as Owen forcefully states:

All other ways of mortification are vain, all helps leave us helpless; it must be done by the Spirit…Mortification by self-strength, carried on by ways of self-invention, unto the end of a self-righteousness, is the soul and substance of all false religion in the world.

4. The true duty is mortifying the sins of the body.

a. “The body” – Owen explains, when Paul uses the term “body” here, it is synonymous with “the flesh” (mentioned in the same verse). “The flesh” is Paul’s shorthand way of talking about our corrupt and depraved natures. In our fallen condition, our physical bodies are the seat of our corrupt affections and, in great part, the physical members of our body are the instruments of sin.

b. “The deeds of the body” – The deeds of the body are outward sinful actions, some of which are enumerated in Galatians 5:19-21, and called “works of the flesh.” Owen is quick to note, however, that though Paul speaks here of outward actions, they spring from inward causes. Earlier Paul speaks of the mind set on the flesh (Romans 8:6), and elsewhere speaks of the “passions and desires” of the flesh (Galatians 5:24). In chapter seven of Romans, Paul acknowledges that his covetous actions flow from the “sin that dwells within” him (7:17), a sinful principle or power “that dwells in [Paul’s] members” (7:23). Therefore, in order to mortify the outward deeds, one must lay the ax to the root of the tree, killing the inward inclinations to sin.

c. “Put to death the deeds of the body” – Paul is using a metaphor here. To kill something is to take away its strength, vigor, and power so that it cannot exert itself anymore. Owen explains that indwelling sin is compared to a person, elsewhere called “the old man,” who must be put to death. Owen says, when a person is regenerated by the Spirit of God “a principle contrary to [our flesh] and destructive of it (Gal. 5:17) is planted in our hearts.” When we are born again we can confidently say we are crucified with Christ and dead with Him (Romans 6:6,8), but this sin-slaying power planted in our hearts by the Holy Spirit does not eradicate the presence of sin altogether. The Spirit ends sin’s dominion. We must progressively kill sin throughout our lives.

5. The true promise is full and eternal life.

Paul writes, when you perform this sin-killing duty, “you will live.” Owen says, this life not only includes eternal life in the hereafter, but “the joy, comfort, and vigor” of our spiritual life in Christ here and now.

Questions for Personal or Group Reflection:

1. Owen presents a primary Biblical motivation for slaying sin: experiencing fullness of life. Have you ever experienced times in your life when unmortified sin robbed you of “the joy, comfort, and vigor” of your life in Christ?

2. If it’s true that there is “no condemnation” for those who are in Christ (Romans 8:1), how can we take seriously Paul’s warning to Christians that “if you live according to the flesh you will die” (8:13)? Read through Romans 8:1-17 to try to understand more about what Paul is saying.

3. How can you tell the difference between slaying sin by the power of the Spirit and slaying sin through sheer willpower?

. . . .

Read all the posts in this series:

Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 13, Part 14, and Part 15

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