John Calvin Commentary Genesis 27:33

"And Isaac trembled very exceedingly, and said, Who then is he that hath taken venison, and brought it me, and I have eaten of all before thou camest, and have blessed him? Yea, [and] he shall be blessed." — Genesis 27:33 (ASV)

And Isaac trembled very exceedingly. Here again, the faith that had been smothered in the breast of the holy man shines forth and emits fresh sparks, for there is no doubt that his fear springs from faith.

Besides, it is no common fear that Moses describes, but one that utterly confounds the holy man. For, since he was perfectly conscious of his own vocation and therefore was persuaded that the duty of naming the heir with whom he should deposit the covenant of eternal life was divinely commanded of him, he no sooner discovered his error than he was filled with fear that in an affair so great and so serious God had allowed him to err.

For unless he had thought that God was the director of this act, what would have hindered him from alleging his ignorance as an excuse, and from becoming enraged against Jacob, who had stolen in upon him by fraud and by unjustifiable tactics?

But although covered with shame because of the error he had committed, he nevertheless, with a collected mind, ratifies the benediction he had pronounced; and I do not doubt that he then, as one awakening, began to recall the oracle to which he had not been sufficiently attentive.

Therefore, the holy man was not impelled by ambition to be so tenacious of his purpose, as obstinate men usually are, who pursue to the end what they have once, though foolishly, begun.

But the declaration, I have blessed him, yea, and he shall be blessed, was the effect of a rare and precious faith. For he, renouncing the affections of the flesh, now yields himself entirely to God and, acknowledging God as the Author of the benediction he had uttered, ascribes due glory to him by not daring to retract it.

The benefit of this doctrine pertains to the whole Church, so that we may certainly know that whatever the heralds of the gospel promise to us by the command of God will be efficacious and stable, because they do not speak as private individuals, but by the command of God himself; and the infirmity of the minister does not destroy the faithfulness, power, and efficacy of God’s word.

He who presents himself to us, charged with the offer of eternal happiness and life, is subject to our common miseries and to death; yet, nevertheless, the promise is efficacious. He who absolves us from sins is himself a sinner; but because his office is divinely assigned to him, the stability of this grace, having its foundation in God, will never fail.