Calvin's Commentaries, Vol. 5: Harmony of the Law, Part III, tr. by John King, [1847-50], at sacred-texts.com
Sanctions of the Law
contained in the Promises and Threats
We now come to the conclusion of the Exposition of the Law, wherein we are to treat of the sanctions of it contained both in the promises and threats. For, although God might in His own right simply require what He pleased, yet such is His kindness to men, that He chose to entice them by promises to obey Him freely. Since, therefore, we are naturally attracted by the hope of reward, we are slow and lazy, until some fruit appears. Consequently God voluntarily promises, in order to arouse them from their sloth, that if men obey His Law, He will repay them. Nor is this an ordinary act of liberality that He prefers to agree with us for the payment of a recompense, rather than simply to command by His sovereignty. For we must bear in mind the declaration of Christ, that when we have fulfilled the whole Law, we still deserve nothing; since God claims for Himself our entire services. (Lu 17:10.) However we may strive, therefore, even beyond our strength, and devote ourselves entirely to keep the Law, still God lies under no obligation to us, except in so far as He has Himself voluntarily agreed, and made Himself our spontaneous debtor. And this has been pointed out even by the common theologians, that the reward of good works does not depend upon their dignity or merit, but upon His covenant. 194 Still, as we shall soon see, such promises would not avail us the least if God rewarded every one according to his works; but, because this defect is adventitious, God’s great mercy nevertheless shines forth in the fact that he has deigned to encourage us to obedience by setting before us the hope of eternal life. And hence He reproves the ingratitude of the Israelites by Eze 20:21; because they had despised His good commandments, of which it was said that “if a man do them, he should live in them.”
We now perceive how the authority of the Law was confirmed by the promises; but because we are not only indolent but also refractory, He added on the other side threats which might inspire terror, both to subdue the obstinacy of the flesh and to correct the security in which we are too apt to indulge. It will be expedient now to treat of both.
“Sur ceste paction, que Dieu en a faite;” but upon that agreement which God has made to give it. — Fr. Bishop Davenant, after quoting William Archbishop of Paris, Aquinas, and Durandus, to the same effect, says, “To these may be added Scotus, Gregory, Occam, Gabriel, (Biel,) Alfonsus, and very many others of the better class of writers among the Romanists, who avowedly maintain that the works of the righteous, wrought by the assistance of grace, do not on that account acquire any intrinsic worthiness for life eternal; but that, as regards this reward, it depends entirely upon the gracious acceptance and promise of God.” — Disputatio de Justitia. Allport’s Transl., vol. 2, p. 70.