GENERAL PRINCIPLES FOR THE RESTORATION AND PROMOTION OF
THE SACRED LITURGY
1. The Nature of the Sacred Liturgy and Its Importance in the Church's Life
5. God who "wills that all men be saved and come to the knowledge of the truth" (1 Tim. 2:4), "who in many and various ways spoke in times past to the fathers by the prophets" (Heb. 1:1), when the fullness of time had come sent His Son, the Word made flesh, anointed by the Holy Spirit, to preach the the gospel to the poor, to heal the contrite of heart , to be a "bodily and spiritual medicine" , the Mediator between God and man . For His humanity, united with the person of the Word, was the instrument of our salvation. Therefore in Christ "the perfect achievement of our reconciliation came forth, and the fullness of divine worship was given to us" .
The wonderful works of God among the people of the Old Testament were but a prelude to the work of Christ the Lord in redeeming mankind and giving perfect glory to God. He achieved His task principally by the paschal mystery of His blessed passion, resurrection from the dead, and the glorious ascension, whereby "dying, he destroyed our death and, rising, he restored our life" . For it was from the side of Christ as He slept the sleep of death upon the cross that there came forth "the wondrous sacrament of the whole Church" .
6. Just as Christ was sent by the Father, so also He sent the apostles, filled with the Holy Spirit. This He did that, by preaching the gospel to every creature , they might proclaim that the Son of God, by His death and resurrection, had freed us from the power of Satan  and from death, and brought us into the kingdom of His Father. His purpose also was that they might accomplish the work of salvation which they had proclaimed, by means of sacrifice and sacraments, around which the entire liturgical life revolves.
Thus by baptism men are plunged into the paschal mystery of Christ: they die with Him, are buried with Him, and rise with Him ; they receive the spirit of adoption as sons "in which we cry: Abba, Father" ( Rom. 8 :15), and thus become true adorers whom the Father seeks . In like manner, as often as they eat the supper of the Lord they proclaim the death of the Lord until He comes . For that reason, on the very day of Pentecost, when the Church appeared before the world, "those who received the word" of Peter "were baptized." And "they continued steadfastly in the teaching of the apostles and in the communion of the breaking of bread and in prayers . . . praising God and being in favor with all the people" (Acts -47). From that time onwards the Church has never failed to come together to celebrate the paschal mystery: reading those things "which were in all the scriptures concerning him" (Luke 24:27), celebrating the eucharist in which "the victory and triumph of his death are again made present" , and at the same time giving thanks "to God for his unspeakable gift" (2 Cor. 9:15) in Christ Jesus, "in praise of his glory" (Eph. 1:12), through the power of the Holy Spirit.
7. To accomplish so great a work, Christ is always present in His Church, especially in her liturgical celebrations. He is present in the sacrifice of the Mass, not only in the person of His minister, "the same now offering, through the ministry of priests, who formerly offered himself on the cross" , but especially under the Eucharistic species. By His power He is present in the sacraments, so that when a man baptizes it is really Christ Himself who baptizes . He is present in His word, since it is He Himself who speaks when the holy scriptures are read in the Church. He is present, lastly, when the Church prays and sings, for He promised: "Where two or three are gathered together in my name, there am I in the midst of them" (Matt. ) .
Christ indeed always associates the Church with Himself in this great work wherein God is perfectly glorified and men are sanctified. The Church is His beloved Bride who calls to her Lord, and through Him offers worship to the Eternal Father.
Rightly, then, the liturgy is considered as an exercise of the priestly office of Jesus Christ. In the liturgy the sanctification of the man is signified by signs perceptible to the senses, and is effected in a way which corresponds with each of these signs; in the liturgy the whole public worship is performed by the Mystical Body of Jesus Christ, that is, by the Head and His members.
From this it follows that every liturgical celebration, because it is an action of Christ the priest and of His Body which is the Church, is a sacred action surpassing all others; no other action of the Church can equal its efficacy by the same title and to the same degree.