Romans 6:6

6.That our old man, etc. The old man, as the Old Testament is so called with reference to the New; for he begins to be old, when he is by degrees destroyed by a commencing regeneration. But what he means is the whole nature which we bring from the womb, and which is so incapable of the kingdom of God, that it must so far die as we are renewed to real life. This old man, he says, is fastened to the cross of Christ, for by its power he is slain: and he expressly referred to the cross, that he might more distinctly show, that we cannot be otherwise put to death than by partaking of his death. For I do not agree with those who think that he used the word crucified, rather than dead, because he still lives, and is in some respects vigorous. It is indeed a correct sentiment, but not suitable to this passage. The body of sin, which he afterwards mentions, does not mean flesh and bones, but the corrupted mass; for man, left to his own nature, is a mass made up of sin. (188)

He points out the end for which this destruction is effected, when he says, so that we may no longer serve sin. It hence follows, that as long as we are children of Adam, and nothing more than men, we are in bondage to sin, that we can do nothing else but sin; but that being grafted in Christ, we are delivered from this miserable thraldom; not that we immediately cease entirely to sin, but that we become at last victorious in the contest.