John Calvin Commentary Romans 4:21

"and being fully assured that what he had promised, he was able also to perform." — Romans 4:21 (ASV)

That what He had promised, etc. As all people acknowledge God’s power, Paul seems to say nothing very extraordinary about the faith of Abraham; but experience proves that nothing is more uncommon or more difficult than to ascribe to God’s power the honor it deserves. Indeed, there is no obstacle, however small and insignificant, by which the flesh imagines God’s hand is restrained from working.

Therefore, in the slightest trials, the promises of God slip away from us. When there is no challenge, it is true, no one, as I have said, denies that God can do all things; but as soon as anything comes to hinder the course of God’s promise, we cast down God’s power from its eminence.

Therefore, so that God’s power may receive from us its due right and honor, when a challenge arises, we should resolve this: that His power is as capable of overcoming the world’s obstacles as the sun’s strong rays are of dissipating mists.

We are indeed usually accustomed to excuse ourselves, saying that we detract nothing from God’s power whenever we doubt His promises. We commonly say, “The thought that God promises more in His word than He can perform (which would be a falsehood and blasphemy against Him) is by no means the cause of our hesitation; rather, it is the defect we feel in ourselves.” But we do not sufficiently exalt the power of God unless we believe it to be greater than our weakness.

Faith, then, should not focus on our weakness, misery, and defects, but should fix its attention entirely on the power of God alone. For if faith depends on our righteousness or worthiness, it can never rise to consider God’s power. And it is a proof of the unbelief he had previously spoken of, when we measure the Lord’s power by our own standard.

For faith does not merely think that God can do all things, and then, in its own conception, leave Him sitting still. On the contrary, faith regards His power as being in continual exercise and applies it, especially, to the fulfillment of His word. For the hand of God is always ready to perform whatever He has declared by His mouth.

It seems strange to me that Erasmus approved of the relative pronoun in the masculine gender; for although the meaning is not changed, we can still come closer to Paul’s Greek wording. The verb, I know, is passive, but the abruptness can be lessened with a small change.