Romans 6:6-9 — Knowing this, that our old man is crucified with Him, that the body of sin might be destroyed, that henceforth we should not serve sin.
For he that is dead is freed from sin.
Now if we be dead with Christ, we believe that we shall also live with Him:
Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over Him.
body of sin = power acting through the members of the body
destroyed — should be "rendered inactive" — because of our death with Christ, our bodies have been rendered inactive as instruments of sin. The source of sin is the will, but it uses the body as its instrument.
serve = bondage, slavery with no choice of kind or length of service
freed = justified in the legal sense
There is no legitimate method of terminating sin's claims except by death. Death both snaps all bonds and annuls all obligations. The statement of this verse [verse 7] covers the whole of the preceding argument and does not apply merely to the figure of bondage just mentioned. The special reference is to the subject of crucifixion, the death penalty which Christ endured. Our identification with Chirst, as the One who endured the penalty for us, removes the legal sentence from us and thereby delivers us from a condition of bondage to sin. There is both the removal of the penalty and the deliverance from the power. A corpse can neither be punished nor can it become subservient to the will of another. (Vine, The Epistle to the Romans, pg. 90)
If (verse eight) — inevitable result. Once we are saved, we live with Christ regardless of our own effort.
dominion = power of a lord
Sanctification is not primarily a matter of striving to live holy, but of knowing that we are holy in Christ.
Paul's way is always: doctrine first, then the application. We find this even within sections of his epistles [as in these four verses]. In the larger context it is the same. The "old man" has been crucified and buried with Christ; now accept this by faith and bury that "dead body" — experientially. We have this idea again in Colossians 3:9-10 and Ephesians 4:22, 24. The former passage states, "ye have put off the old man … and have put on the new man … " while the latter exhorts, "… put off … the old man … and … put on the new man … " The former refers to a positional fact, the latter to the practical application of that fact. (Stam, The Epistle of Paul to the Romans, pg. 146-147)
Don't bemoan your sinful state, rejoice in your glorious standing in Christ. This is faith, not works. We quit serving sin — we reckon it dead — victory lies not in struggling but in appreciation of the fact. The battle has already been won in Christ.