39 “Give ye glory to God, above Israel is the magnificence of Him”. Of whom says the Apostle, “Upon the Israel of God.” For “not all that are out of Israel, are Israelites:” for there is also an Israel after the flesh. Whence he says, “See ye Israel after the flesh.” “For not they that are sons of the flesh, are sons of God, but sons of promise are counted for a seed.” Therefore at that time when without any intermixture of evil men His people shall be, like a heap purged by the fan, like Israel in whom guile is not, then most pre-eminent “above Israel” shall be “the magnificence” of “Him: and the virtue of Him in the clouds.” For not alone He shall come to judgment, but with the elders of His people: to whom He has promised that they shall sit upon thrones to judge, who even shall judge angels. These be the clouds.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)