12 “Blessed is the nation whose God is the Lord:” one nation is blessed, belonging to the heavenly city, which has not chosen save the Lord for their God: “And the people whom He has chosen for His own inheritance”: and which not of itself, but by the gift of God, has been chosen, that He by possessing it may not suffer it to be uncared for and miserable.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)