Through union with Christ in his death, says Paul, our old self was put to death with him so that our sinful body might be brought to nothing and cease to be the decisive controlling factor of our lives. This is one aspect of the change in us that is called regeneration.
Here, speaking of the sinful body, Paul is not referring to the physical frame; he means a persons total self, a human individual. “Body,” like “soul,” can signify the whole person in Scripture, and there are traces of this broadened meaning in our ordinary speech. Perhaps you know the word boss derives from the words body masterthe title given to a person in charge of a slave gang. And when we speak colloquially of so many “bods” (or bodies), we mean so many people.
So when Paul speaks of the sinful body, he means the sinful selfthe sinful person I was in my natural, fallen state with my God-dishonoring, self-serving, sin-dominated disposition. That, says Paul, was brought to an end by my union with Christ in his death. The person I used to be was crucified with Christ so that my sinful self (disposition, character) might be brought to nothing, so that from now on I would no longer be sins slave, living under sins domination. I am a new person now, for Christs inclination and instinct to love and serve and honor his heavenly Father has also become the core of my character through my union with him in his risen life.
It is important to understand that this is the work of God. We are to consider ourselves “dead to sin and alive to God in Christ Jesus” (Rom. 6:11) because God has made us so, and this radical change that he has worked in us now has to be lived out. So henceforth we must crucify and mortify each sinful habit that once held us captive (Rom. 8:13), and use all our liberated powers to serve God in righteousness (Rom. 6:12-13; 12:1-2)something that we could not do before.