Hebrews 11:20

20.By faith Isaac, etc. It was also the work of faith to bless as to future things; for when the thing itself does not exist and the word only appears, faith must necessarily bear rule. But first we must notice of what avail is the blessing of which he speaks. For to bless often means to pray for a blessing. But the blessing of Isaac was very different; for it was as it were an introduction into the possession of the land, which God had promised to him and his posterity. And yet he had nothing in that land but the right of burial. Then strange seemed these high titles, “Let people serve thee, and tribes bow down to thee,” (Genesis 27:29;) for what dominion could he have given who himself was hardly a free man? We hence see that this blessing depended on faith; for Isaac had nothing which he could have bestowed on his children but the word of God.

It may, however, be doubted whether there was any faith in the blessing given to Esau, as he was a reprobate and rejected by God. The answer is easy, for faith mainly shone forth, when he distinguished between the two twins born to him, so that he gave the first place to the younger; for following the oracle of God, he took away from the firstborn the ordinary right of nature. And on this depended the condition of the whole nation, that Jacob was chosen by God, and that this choice was sanctioned by the blessing of the father.