10 “Let mount Zion rejoice, and the daughters of Judah be glad, because of Your judgments, O Lord”. O mount Zion, O daughters of Judah, you labour now among tares, among chaff, among thorns ye labour: yet be glad because of God's judgments. God errs not in judgment. Live ye separate, though separate you were not born; not vainly has a voice gone forth from your mouth and heart, “Destroy not my soul with sinners, nor my life with bloody men.” He shall winnow with such art, carrying in His hand a fan, that not one grain of wheat shall fall into the heap of chaff prepared to be burned, nor one beard of chaff pass to the heap to be laid up in the garner. Be glad, O you daughters of Judæa, because of the judgments of God that errs not, and do not yet judge rashly.
To you let it belong to collect, to Him let it belong to separate. But think not that the “daughters of Judah” are Jews. Judah is confession; all the sons of confession are all the sons of Judah. For “salvation is of the Jews,” is nothing else than that Christ is of the Jews. This says also the Apostle, “He is not a Jew which is one outwardly; neither is that circumcision which is outward in the flesh: but he is a Jew which is one inwardly, and circumcision is that of the heart, in the spirit, and not in the letter, whose praise is not of men, but of God.” Be such a Jew; glory in the circumcision of the heart, though you have not the circumcision of the flesh. Let the daughters of Judah be glad, because of Your judgments, O Lord.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)