2 This Psalm is a “Song of degrees;” as we have often said to you, for these degrees are not of descent, but of ascent. He therefore longs to ascend. And whither does he wish to ascend, save into heaven? What means, into heaven? Does he wish to ascend that he may be with the sun, moon, and stars? Far be it! But there is in heaven the eternal Jerusalem, where are our fellow citizens, the Angels: we are wanderers on earth from these our fellow citizens. We sigh in our pilgrimage; we shall rejoice in the city. But we find companions in this pilgrimage, who have already seen this city herself; who summon us to run towards her. At these he also rejoices, who says, “I rejoiced in them who said unto me, We will go into the house of the Lord”...
Source: The Enarrations, or Expositions, on the Psalms (New Advent)