6 “A way You have made in the sight of her, and hast planted the roots of her, and she has filled the land”. Would she have filled the land, unless a way had been made in the sight of her? What was the way which was made in the sight of her? “I am,” He says, “the Way, the Truth, and the Life.” With reason she has filled the land. That has now been said of this vineyard, which has been accomplished at the last. But in the mean time what? “She has covered the mountains with her shadow, and with her branch the cedars of God”.
“You have stretched out her boughs even unto the sea, and even unto the river her shoots”. This requires the office of an expositor, that of a reader and praiser does not suffice: aid me with attention; for the mention of this vineyard in this Psalm is wont to overcloud with darkness the inattentive....But nevertheless the first Jewish nation was this vine. But the Jewish nation reigned as far as the sea and as far as the river. As far as the sea; it appears in Scripture that the sea was in the vicinity thereof.
And as far as the river Jordan. For on the other side of Jordan some part of the Jews was established, but within Jordan was the whole nation. Therefore, “even unto the sea and even unto the river,” is the kingdom of the Jews, the kingdom of Israel: but not “from sea even unto sea, and from the river even unto the ends of the round world;” this is the future perfection of the vineyard, concerning which in this place he has foretold. When, I say, he had foretold to you the perfection, he returns to the beginning, out of which the perfection was made.
Of the beginning will you hear? “Even unto the river.” Of the end will you hear? “He shall have dominion from sea even unto sea:” that is, “she has filled the earth.” Let us look then to the testimony of Asaph, as to what was done to the first vineyard, and what must be expected for the second vineyard, nay to the same vineyard....What then, the vineyard before the sight whereof a way was made, that she should fill the earth, at first was where? “Her shadow covered the mountains.”
Who are the mountains? The Prophets. Why did her shadow cover them? Because darkly they spoke the things which were foretold as to come. You hear from the Prophets, Keep the Sabbath day, on the eighth day circumcise a child, offer sacrifice of ram, of calf, of he-goat. Be not troubled, her shadow does cover the mountains of God; there will come after the shadow a manifestation. “And her shrubs the cedars of God,” that is, she has covered the cedars of God; very lofty, but of God. For the cedars are types of the proud, that must needs be overthrown. The “cedars of Lebanon,” the heights of the world, this vineyard did cover in growing, and the mountains of God, all the holy Prophets and Patriarchs.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)