verse 4. That the justification of the law might be fulfilled, etc. They who understand that the renewed, by the Spirit of Christ, fulfil the law, introduce a gloss wholly alien to the meaning of Paul; for the faithful, while they sojourn in this world, never make such a proficiency, as that the justification of the law becomes in them full or complete. This then must be applied to forgiveness; for when the obedience of Christ is accepted for us, the law is satisfied, so that we are counted just. For the perfection which the law demands was exhibited in our flesh, and for this reason — that its rigor should no longer have the power to condemn us. But as Christ communicates his righteousness to none but to those whom he joins to himself by the bond of his Spirit, the work of renewal is again mentioned, lest Christ should be thought to be the minister of sin: for it is the inclination of many so to apply whatever is taught respecting the paternal kindness of God, as to encourage the lasciviousness of the flesh; and some malignantly slander this doctrine, as though it extinquished the desire to live uprightly.
—Calvin, Commentary on Romans 8:4 (HT: Jack Miller)