The word mortification comes from the root word mort, which has to do with death and dying. In English, the word mortification is often used to describe a feeling of shame or embarrassment, but that is not the meaning used when we say "mortification of sin" or of the flesh. Instead, the word is used to denote the killing of the sin nature, or the subduing of the flesh.
What is mortification of the flesh or mortification of sin?
The word mortify appears only in the King James Version of the Bible, in two verses. The first is Romans 8:13, which says, "For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live" (KJV). The second is, "Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry" (Colossians 3:5 KJV). In more modern versions, the word mortify is translated "put to death."
In this verse, we see the basic difference between the life of a believer and the life of an unbeliever. The believer is encouraged to put to death the deeds of the flesh—what Paul calls "the deeds of the body" (Romans 8:13) or "what is earthly in you" (Colossians 3:5). Paul defines "what is earthly in you" as "sexual immorality, impurity, passion, evil desire, and covetousness, which is idolatry" (Colossians 3:5). The person who is ruled by these things is said to be "in the flesh" and to have his mind set on the flesh, which is death (Romans 8:5-6). But the believer sets his mind on the Spirit, and the things of the Spirit, which is life and peace (Romans 8:5-6). The reason for this is found in the very next verse: "For the mind that is set on the flesh is hostile to God, for it does not submit to God's law; indeed, it cannot" (Romans 8:7).
This is a question of nature. A cat will do cat things: it will chase mice, and purr, and sit on your lap. A frog will do frog things: jump, and croak, and sit on a lily pad. But cats do not do frog things, and vice versa. It is not in their nature. A similar thing is true of believers and unbelievers. Believers will mortify the flesh because the flesh is opposed to the Spirit which indwells them; it is against their nature to follow the flesh. "For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh, for these are opposed to each other, to keep you from doing the things you want to do" (Galatians 5:17). This does not mean we always succeed—the pull of the flesh is powerful. That is why we are told to take action against it, to "mortify" it, to put it to death.
Jesus made several statements about this believer's "death in life" paradox. He said, "Truly, truly, I say to you, unless a grain of wheat falls into the earth and dies, it remains alone; but if it dies, it bears much fruit. Whoever loves his life loses it, and whoever hates his life in this world will keep it for eternal life" (John 12:24-25). Jesus' life on Earth was one of purposeful death; His followers live under the same principle. We may not be martyred in a dramatic way, but the Christian life follows a pattern of death to self, and life to God. That is why Paul quoted the Psalmist, saying "For your sake we are being killed all the day long; we are regarded as sheep to be slaughtered" (Romans 8:36). We look forward to the next life as the true life, and for that reason, we separate ourselves from this world. The result of this attitude is often suffering, but the Bible makes it clear that this is normal, even comparing us to soldiers on a foreign battlefield. "Share in suffering as a good soldier of Christ Jesus. No soldier gets entangled in civilian pursuits, since his aim is to please the one who enlisted him" (2 Timothy 2:3).
The mortification of sin and the flesh is a deep and complex issue in the Christian life, and it is hard to sum it up in one short article. But we know that every believer will go through it, for it is in their nature to follow the Spirit, and the Spirit is not at home in this world. Over and over again, Christians find themselves at crossroads—one sign pointing to "this world" and the other pointing to "the next world." The decision was summed up perfectly by Jesus, who said: "Enter by the narrow gate. For the gate is wide and the way is easy that leads to destruction, and those who enter by it are many. For the gate is narrow and the way is hard that leads to life, and those who find it are few" (Matthew 7:13-14).
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