From the stem of Jesse, according to the prophecy of Isaias, there came forth a most fair flower, and that flower was Christ. It is therefore only natural that there should be a continuity between the liturgy of the synagogue and that of the Christian faith. The authority of Imperial Rome even confused the Christians with the Jews; during the transitional period the Christian family, presenting the outward and legal appearance of a Jewish community, borrowed there from likewise various liturgical usages which still form part of her Sacred patrimony, and, like her faith, are, so to speak, of the seed of Abraham and of Israel by origin and descent.
The Roman Advent bore a joyful character; now we regard this season as a penitential time, or at least, a time in which the absence of Christ is stressed in the Liturgy. It is a season of preparation, because during all the years before the birth of Our Savior, the events of human history led up to this central fact.
The chants of the Mass, the responsories, the antiphons of the divine Office, all contain Alleluias. The Gloria in excelsis is omitted from the ferial Masses until Christmas. It would seem that the whole of nature, looking forward, as the Apostle describes it, to the last judgment, awaiting the revelation of the Son of God, feels herself uplifted by the Incarnation of the Word of God, Who, after so many ages of waiting, comes at length into this world to bring His greatest handiwork to its final perfection.
The Sacred Liturgy, during this time, gathers from the Scriptures all those passages which are most forcible and best adapted to express the intense and joyful longing with which the holy patriarchs, the prophets and the just men of the Old Testament hastened by their prayers the coming of the Son of God. We cannot do better than associate ourselves with their pious feelings, and pray the Word made Flesh that He will deign to be born in the hearts of all men and spread His kingdom likewise throughout those many lands where His holy Name has not hitherto been made known, and whose inhabitants still sleep in darkness and the shadow of death.
The Roman Missal today begins the liturgical cycle. The Incarnation is the true central point which divides the course of the ages. By this period of preparation called Advent, the ages before Christ and leading us to His birth are recalled; following the feast of Christmas the great events in the life of Christ and the ages that lead toward the final judgment are kept in mind. The Missal, therefore, is logical and corresponds closely to this lofty concept of history, by which the Incarnation is made the true central event in the world's drama.
The spirit of the sacred Liturgy during Advent, full of the joyful announcement of approaching freedom, is one of holy enthusiasm, tender gratitude, and an intense longing for the coming of the Word of God in the hearts of all the children of Adam. Man is made up of spirit and flesh, and whilst the former desirous of being drawn towards truth and love, the latter understands only such good or evil as can be perceived by the senses, and must therefore be held in check by penance and by a salutary fear of the judgments of almighty God.– The Roman Missal