Gregory of Nyssa

And where shall we place that oracle of Isaiah, which cries to the wilderness, "Be glad, O thirsty wilderness. Let the desert rejoice and blossom as a lily, and the desolate places of Jordan shall blossom and shall rejoice"? For it is clear that it is not to places without soul or sense that he proclaims the good tidings of joy, but he speaks, by the figure of the desert, of the soul that is parched and unadorned.

And "the excellence of Carmel" is given to the soul that bears the likeness to the desert, that is, the grace bestowed through the Spirit. For since Elijah dwelt in Carmel, and the mountain became famous and renowned by the virtue of him who dwelt there, and since moreover John the Baptist, illustrious in the spirit of Elijah, sanctified the Jordan, therefore the prophet foretold that "the excellence of Carmel" should be given to the river.

And "the glory of Lebanon," from the similitude of its lofty trees, he transfers to the river. For as great Lebanon presents a sufficient cause of wonder in the very trees that it brings forth and nourishes, so is the Jordan glorified by regenerating people and planting them in the paradise of God. And of them, as the words of the psalmist say, ever blooming and bearing the foliage of virtues, "the leaf shall not wither," and God shall be glad, receiving their fruit in due season, rejoicing, like a good planter, in his own works.