John Calvin Commentary Romans 8:12

"So then, brethren, we are debtors, not to the flesh, to live after the flesh:" — Romans 8:12 (ASV)

So then, brethren, etc. This is the conclusion of what has been previously said. For if we are to renounce the flesh, we ought not to consent to it; and if the Spirit ought to reign in us, it is inconsistent not to attend to His guidance. Paul’s sentence is here defective, for he omits the other part of the contrast—that we are debtors to the Spirit; but the meaning is in no way obscure.

This conclusion has the force of an exhortation, for he is always accustomed to draw exhortations from his doctrine. So in another place, Ephesians 4:30, he exhorts us

not to grieve the Spirit of God, by whom we have been sealed to the day of redemption:

He does the same in Galatians 5:25,

If we live in the Spirit, let us also walk in the Spirit.

And this is the case when we renounce carnal lusts so as to devote ourselves, as those who are bound, to the righteousness of God. Thus indeed we ought to reason, not as some blasphemers are accustomed to do, who talk idly and say—that we must do nothing because we have no power. But it is, as it were, to fight against God when we extinguish the grace offered to us by contempt and negligence.