Thomas Aquinas, on Ps 49:4

“He shall call heaven from above, and the earth, to judge his people.”

“"He has called heaven from above," etc. Having set forth the coming of the judge to judgment and the preparation of the judge with respect to the instrument of punishment, here he sets forth the preparation for the judgment with respect to the ministers. And first he treats of the attendance of the ministers; second, of the office of the Angels, at "Gather together"; third, of the office of the apostles, at "It shall be announced." In the first part, mention is made of heaven and earth. And this is understood in two ways. In one way, it is understood by metonymy, the container for the contained, so that by "heaven" he designates the saints who are in heaven, and by "earth" he designates men who are on earth; and all of these are called to judgment. And this is the second calling, because above he said, "And he called the earth," because that calling is the calling to faith, to which all are called, good and bad. Mt. 13: "The kingdom of heaven is like a net cast into the sea," etc. But this second calling is for separating, because "they chose the good into their vessels, and cast the bad forth." And therefore he says, "to discern his people," by the separation of the good from the bad. Mt. 25: "He shall separate the sheep from the goats." Ps. 42: "Judge me, O God, and distinguish my cause." But the heavens are called differently from the earth; because heavenly men are called for this purpose as judges. Mt. 19: "You who have left all things," etc., up to "the tribes of Israel." The earthly are called to be judged. Joel 3: "I will gather all nations and bring them down into the valley of Jehoshaphat." Or, "he called heaven," that is, the heavenly, that is, the just, to their reward. Dan. 12: "The learned shall shine like the brightness of the firmament," etc. "And the earth," that is, the earthly, that is, the wicked, to punishment. There can also be another sense, so that heaven and earth stand for the corporeal creatures themselves; and thus they are called by way of testimony or assault against the unfaithful, because in them the wicked were able to perceive from heaven and earth. Job 20: "The heavens shall reveal his iniquity, and the earth shall rise up against him," namely against the sinner. Or, "he called heaven from above," to give up the souls of the saints which it holds, and the earth, to give up the souls of the wicked which it holds in the depths.”

Imported from an open dataset — not yet checked against the printed edition.