John Calvin Commentary Romans 6:12

"Let not sin therefore reign in your mortal body, that ye should obey the lusts thereof:" — Romans 6:12 (ASV)

Let not sin then, etc. He now begins with an exhortation, which naturally arises from the doctrine he delivered regarding our fellowship with Christ. Though sin dwells in us, it is inconsistent for it to be so vigorous as to exercise its reigning power; for the power of sanctification should be superior to it, so that our life may testify that we are truly the members of Christ.

I have already reminded you that the word body is not to be taken for flesh, skin, and bones, but, so to speak, for the whole of what man is. This may undoubtedly be inferred from the passage, for the other clause, which he immediately adds regarding the members of the body, also includes the soul. Thus, Paul designates earthly man in a disparaging manner, for, owing to the corruption of our nature, we aspire to nothing worthy of our origin.

So also God says in Genesis 6:3, where He complains that man had become flesh like the brute animals, and thus He attributes to him nothing but what is earthly. To the same purpose is the declaration of Christ, What is born of the flesh is flesh (John 3:6). But if anyone makes this objection—that the case with the soul is different—the ready answer to this is that in our present degenerate state, our souls are fixed to the earth and so enslaved to our bodies that they have fallen from their own superiority.

In a word, the nature of man is said to be corporeal because he is destitute of celestial grace and is only a kind of empty shadow or image. We may add that the body, by way of contempt, is said by Paul to be mortal, and this is to teach us that the whole nature of man tends toward death and ruin.

Still further, he gives the name of sin to the original depravity which dwells in our hearts, which leads us to sin, and from which indeed all evil deeds and abominations stream forth. In the middle, between sin and us, he places lusts, as the former has the office of a king, while lusts are its edicts and commands.