6 Thus also most pertinently may be understood, “let the mountains bear peace to the people,” namely, that we understand the peace to consist in the reconciliation whereby we are reconciled to God: for the mountains receive this for His people....“Let the mountains, therefore, receive peace for the people, and the hills justice:” so that in this manner, both being at one, there may come to pass that which has been written, “justice and peace have kissed one another.” But that which other copies have, “let the mountains receive peace for the people, and let the hills:” I think must be understood of all sorts of preaching of Gospel peace, whether those that go before, or those that follow after. But in these copies this follows, “in justice He shall judge the poor of the people.” But those copies are more approved of which have that which we have expounded above, “let the mountains bear peace to the people, and the hills justice.” But some have, “to Your people;” some have not to “Your,” but only “to the people.”
7. “He shall judge the poor of the people, and shall save the sons of the poor”. The poor and the sons of the poor seem to me to be the very same, as the same city is Sion and the daughter of Sion. But if it is to be understood with a distinction, the poor we take to be the mountains, but the sons of the poor the hills: for instance, Prophets and Apostles, the poor, but the sons of them, that is, those that profit under their authority, the sons of the poor. But that which has been said above, “shall judge;” and afterwards, “shall save;” is as it were a sort of exposition in what manner He shall judge. For to this end He shall judge, that He may save, that is, may sever from those that are to be destroyed and condemned, those to whom He gives “salvation ready to be revealed at the” last time. For by such men to Him is said, “Destroy not with ungodly men my soul:” and, “Judge me, O God, and sever my cause from the nation unholy.” We must observe also that he says not, He shall judge the poor people, but, “the poor of the people.” For above when he had said, “to judge Your people in justice and Your poor in judgment,” the same he called the people of God as His poor, that is, only the good and those that belong to the right hand side. But because in this world those for the right and those for the left feed together, who, like lambs and goats at the last are to be put asunder; the whole, as it is mingled together, he has called by the name of the People. And because even here he puts judgment in a good sense, that is, for the purpose of saving: therefore he says, “He shall judge the poor of the people,” that is, shall sever for salvation those that are poor among the people. “And He shall humble the false-accuser.” No false-accuser can be more suitably recognised here than the devil. False accusation is his business. “Does Job worship God gratis?” But the Lord Jesus does humble him, by His grace aiding His own, in order that they may worship God gratis, that is, may take delight in the Lord. He humbled him also thus; because when in Him the devil, that is, the prince of this world, had found nothing, he slew Him by the false accusations of the Jews, whom the false-accuser made use of as his vessels, working in the sons of unbelief....
8. “And He shall endure to the sun,” or, “shall endure with the sun”. For thus some of our writers have thought would be more exactly translated that which in the Greek is συμπαραμενεῖ. But if in Latin it could have been expressed in one word, it must have been expressed by compermanebit: however, because in Latin the word cannot be expressed, in order that the sense at least might be translated, it has been expressed by, “He shall endure with the sun.” For He shall co-endure to the sun is nothing else but, “He shall endure with the sun.” But what great matter is it for Him to endure with the sun, through whom all things were made, and without whom nothing was made, save that this prophecy has been sent before for the sake of those who think that the religion of the Christian name up to a particular time in this world will live, and afterwards will be no more? “He shall endure” therefore “with the sun,” so long as the sun rises and sets, that is, so long as these times revolve, there shall not be wanting the Church of God, that is, Christ's body on earth. But that which he adds, “and before the moon, generations of generations:” he might have expressed by, and before the sun, that is, both with the sun and before the sun: which would have been understood by both with times and before times. That then which goes before time is eternal: and that is truly to be held eternal which by no time is changed, as, “in the beginning was the Word.” But by the moon he has chosen rather to intimate the waxings and wanings of things mortal. Lastly, when he had said, “before the moon,” wishing in a manner to explain for what purpose he inserted the moon, “generations,” he says, “of generations.” As though he were saying, before the moon, that is, before the generations of generations which pass away in the departure and succession of things mortal, like the lunar wanings and waxings. And thus what is better to be understood by His enduring before the moon, than that He takes precedence of all mortal things by immortality? Which also as follows may not impertinently be taken, that whereas now, having humbled the false-accuser, He sits at the right hand of the Father, this is to endure with the sun. For the brightness of the eternal glory is understood to be the Son: as though the Sun were the Father, and the Brightness of Him His Son. But as these things may be spoken of the invisible Substance of the Creator, not as of that visible creation wherein are bodies celestial, of which bright bodies the sun has the pre-eminence, from which this similitude has been drawn: just as they are drawn even from things earthly, to wit, stone, lion, lamb, man having two sons, and the like: therefore having humbled the false-accuser, He endures with the sun: because having vanquished the devil by the Resurrection, He sits at the right hand of the Father, where He dies no more, and death no longer over Him shall have dominion. This too is before the moon, as though the First-born from the dead were going before the Church, which is passing on in the departure and succession of mortals. These are “the generations of generations.” Or perchance it is because generations are those whereby we are begotten mortally; but generations of generations those whereby we are begotten again immortally. And such is the Church which He went before, in order that He might endure before the moon, being the First-born of the dead. To be sure, that which is in the Greek γενεας γενεῶν, some have interpreted, not “generations,” but, “of a generation of generations:” because γενεας is of ambiguous case in Greek, and whether it be the genitive singular της γενε,ς, that is, of the generation, or the accusative plural τὰς γενεὰς, that is, the generations, does not clearly appear, except that deservedly that sense has been preferred wherein, as though explaining what he had called “the moon,” he added in continuation, “generations of generations.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)