Catechism of the Catholic Church
1108 In every liturgical action the Holy Spirit is sent in order to bring us into communion with Christ and so to form his Body. The Holy Spirit is like the sap of the Father's vine which bears fruit on its branches. 26 The most intimate cooperation of the Holy Spirit and the Church is achieved in the liturgy. The Spirit who is the Spirit of communion, abides indefectibly in the Church. For this reason the Church is the great sacrament of divine communion which gathers God's scattered children together. Communion with the Holy Trinity and fraternal communion are inseparably the fruit of the Spirit in the liturgy. 27
1109 The epiclesis is also a prayer for the full effect of the assembly's communion with the mystery of Christ. "The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit" 28 have to remain with us always and bear fruit beyond the Eucharistic celebration. The Church therefore asks the Father to send the Holy Spirit to make the lives of the faithful a living sacrifice to God by their spiritual transformation into the image of Christ, by concern for the Church's unity, and by taking part in her mission through the witness and service of charity.
1110 In the liturgy of the Church, God the Father is blessed and adored as the source of all the blessings of creation and salvation with which he has blessed us in his Son, in order to give us the Spirit of filial adoption.
1111 Christ's work in the liturgy is sacramental: because his mystery of salvation is made present there by the power of his Holy Spirit; because his Body, which is the Church, is like a sacrament (sign and instrument) in which the Holy Spirit dispenses the mystery of salvation; and because through her liturgical actions the pilgrim Church already participates, as by a foretaste, in the heavenly liturgy.
1112 The mission of the Holy Spirit in the liturgy of the Church is to prepare the assembly to encounter Christ; to recall and manifest Christ to the faith of the assembly; to make the saving work of Christ present and active by his transforming power; and to make the gift of communion bear fruit in the Church.
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.