Why shouldn’t Christians continue in sin? For Paul, the answer, in part, is because your old man was crucified with Christ. And God did that to your old man for a reason—
knowing this, that our old man was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin (Rom 6:6).
Your old man was crucified so that “the body of sin might be done away with.”
What is the “body of sin”?
Some commentators cannot accept that Paul would have negative things to say about the physical body. As one wrote, “The problem with this understanding is that it suggests that the body is in some way sinful.” But why would that be a problem?
As you see later in Romans, Paul is definitely concerned with the physical body and the problems it can cause for the believer. For example, Paul thinks the body has lusts:
Therefore do not let sin reign in your mortal body, that you should obey it in its lusts (Rom 6:12).
Every teenager knows this to be true. Do does the alcoholic and drug addict. So does everyone who has ever tried to stick to a diet, or start a new exercise regime. We know the right thing to do, but our bodies want something else.
Paul also says the body can live, implying that it currently lacks the kind of life he has in mind:
But if the Spirit of Him who raised Jesus from the dead dwells in you, He who raised Christ from the dead will also give life to your mortal bodies through His Spirit who dwells in you (Rom 8:11).
For Paul, abundant living depends on putting to death the deeds of the body:
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 (Rom 8:13).
The body has deeds that correspond to its lusts. Instead of feeding those deeds, you need to put them to death.
Paul also hopes that one day our bodies will be redeemed, which implies we’ll have them forever, but only after they have been saved in some way:
Not only that, but we also who have the firstfruits of the Spirit, even we ourselves groan within ourselves, eagerly waiting for the adoption, the redemption of our body (Rom 8:23).
In sum, the body is a huge concern in Paul’s conception of living the Christian life. Sanctification involves the body. For example, Paul says that we must present our bodies to God as you would present a sacrifice:
I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service (Rom 12:1).
So, despite the skepticism of some commentators, I agree with Leon Morris who explained that Paul definitely thought of sanctification “as associated with the body,” so that the expression body of sin means “the body as conditioned and controlled by sin, the sinful body” (Morris, Romans, p. 220). Bodies in and of themselves are not the problem. Paul is not against bodies per se. But after the fall, the body became corrupt, making it a problem for the believer. As Hodges said, “Paul saw the physical body as the seat of sin in the Christian” (Hodges, Romans, p. 171). Yes, temptations come from outside of you, but they also come from within the body itself.
In short, sin attacks you through the body.
Remember, your body is part of a fallen creation, and bound to the powers of this world. As Robertson explained:
Now, this being in the body not only binds us to the rest of creation; it also, as in the case of the [sarx], binds us to the powers which control the body. In creation under the Fall these are the powers of sin and death (Robertson, The Body, p. 30).
So as far as Christian growth is concerned, something must be done about the body. But what?
God’s answer was to crucify the old man with Christ. As Paul says, that crucifixion is meant to “do away” (katargeō) with the body of sin. In what way? The body does not disappear into thin air. And you do not lose your body to become pure spirit. That is not Paul’s point. Instead, the verb for “do away” can mean “to cause something to lose its power or effectiveness, invalidate, make powerless” (BDAG, p. 525) or to “render idle or inactive” (Moulton and Milligan, Vocabulary, p. 331). The crucifixion of the old man means the body of sin—which is full of lusts (cf. Rom 6:12)—can lose its effectiveness as a source of temptation. Instead of being an active source of sin, crucifying of the old man renders it powerless, idle, or inactive.
That does not the body of sin ceases to be a problem. but it does cease to be an overriding power.
Your old man is crucified, which means your body of sin can be inactive. Paul wants the Romans to know that truth about their position so that it can become true of them in their experience.
For Paul, doing away with the body of sin does not mean it is impossible for a Christian to sin, but it does mean that sin is no longer necessary.