Genesis 27:39

39.Behold, thy dwelling shall be the fatness of the earth. At length Esau obtains what he had asked. For, perceiving himself to be cast down from the rank and honor of primogeniture, he chooses rather to have prosperity in the world, separated from the holy people, than to submit to the yoke of his younger brother. But it may be thought that Isaac contradicts himself, in offering a new benediction, when he had before declared, that he had given to his son Jacob all that was placed at his disposal. I answer, that what has been before said concerning Ishmael must be noted in this place. For God, though he hearkened to Abraham’s prayer for Ishmael, so far as concerned the present life, yet immediately restricts his promise, by adding the exception implied in the declaration, that in Isaac only should the seed be called. I do not, however, doubt, that the holy man, when he perceived that his younger son Jacob was the divinely ordained heir of a happy life, would endeavor to retain his firstborn, Esau, in the bond of fraternal connection, in order that he might not depart from the holy and elect flock of the Church. But now, when he sees him obstinately tending in another direction, he declares what will be his future condition. Meanwhile the spiritual blessing remains in its integrity with Jacob alone, to whom Esau refusing to attach himself, voluntarily becomes an exile from the kingdom of God. The prophecy uttered by Malachi, (Malachi 1:3,) may seem to be contradictory to this statement. For, comparing the two brothers, Esau and Jacob, with each other, he teaches that Esau was hated, inasmuch as a possession was given to him in the deserts; and yet Isaac promises him a fertile land. There is a twofold solution: either that the Prophet, speaking comparatively, may with truth call Idumea a desert in comparison with the land of Canaan, which was far more fruitful; or else that he was referring to his own times. For although the devastations of both lands had been terrible, yet the land of Canaan in a short time flourished again, while the territory of Edom was condemned to perpetual sterility, and given up to dragons. Therefore, although God, with respect to his own people, banished Esau to desert mountains, he yet gave to him a land sufficiently fertile in itself to render the promise by no means nugatory. For that mountainous region both had its own natural fruitfulness, and was so watered by the dew of heaven, that it would yield sustenance to its inhabitants.