3 Next there follows, “To judge Your people in justice, and Your poor in judgment”. For what purpose the royal Father gave to the royal Son His judgment and His justice is sufficiently shown when he says, “To judge Your people in justice;” that is, for the purpose of judging Your people. Such an idiom is found in Salomon: “The Proverbs of Salomon, son of David, to know wisdom and discipline:” that is, the Proverbs of Salomon, for the purpose of knowing wisdom and discipline.
So, “Your judgment give Thou, to judge Your people:” that is, “Your judgment” give Thou for the purpose of judging Your people. But that which he says before in, “Your people,” the same he says afterwards in, “Your poor:” and that which he says before in, “in justice;” the same afterward in, “in judgment:” according to that manner of repetition. Whereby indeed he shows, that the people of God ought to be poor, that is, not proud, but humble. For, “blessed are the poor in spirit, for theirs is the kingdom of Heaven.” In which poverty even blessed Job was poor even before he had lost those great earthly riches.
Which thing for this reason I thought should be mentioned, because there are certain persons who are more ready to distribute all their goods to the poor, than themselves to become the poor of God. For they are puffed up with boasting wherein they think their living well should be ascribed to themselves, not to the grace of God: and therefore now they do not even live well, however great the good works which they seem to do....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)