Summary of comments of this office by Dom Schuster, in his work L'année liturgique.

The Introït is taken from Isaias (Ch. 30) with the versicle from Psalm 79, where the Lord is besought to reveal Himself at last before the faithful tribes of Israel. It is the psalm of the "apparitions," which the Church repeats often during the Christmas cycle, because it expresses the supreme desire of the patriarchs and the just: that the "Power on high" come and redeem mankind and put to rout Satan's empire, the "strong army" that jealously guards its prey.

The Gradual is taken from Psalm 49 which, in vivid, striking accents, describes the parousia of the divine Judge, coming into the world accompanied by the multitude of saints, in order to render to each according to his deeds. Between the first coming of the Infant Jesus and the last coming of the Supreme Judge of the living and the dead, there is an intimate connection,of which the Church does not fail to remind us. It is the beginning and the end of the messianic era.

The Alleluia is borrowed from Psalm 121, and, making a delicate allusion to "Sancta Jerusalem," it expresses the joy of the soul at the dawn of its impending return to the heavenly Jerusalem.

The Offertory is taken from Psalm 84, which is clearly messianic. After long centuries of indignation, God at last inaugurates the era of grace and looks upon His people with mildness. The people in turn hopes and prays, that the Father almighty reveal to the world His mercy which is, precisely, Jesus the "Savior."

The antiphon for Communion is taken from Baruch (Ch. 4, 5) which, under the symbol of the Jerusalem of Scripture, invites the soul this day to prepare for the joys which the Lord has in store for Christmas.