CATECHISM OF THE CATHOLIC CHURCH
SECOND EDITION

Paragraphs 1106–1109

1106 Together with the anamnesis, the epiclesis is at the heart of each sacramental celebration, most especially of the Eucharist:

You ask how the bread becomes the Body of Christ, and the wine . . . the Blood of Christ I shall tell you: the Holy Spirit comes upon them and accomplishes what surpasses every word and thought. . . . Let it be enough for you to understand that it is by the Holy Spirit, just as it was of the Holy Virgin and by the Holy Spirit that the Lord, through and in himself, took flesh.

1107 The Holy Spirit's transforming power in the liturgy hastens the coming of the kingdom and the consummation of the mystery of salvation. While we wait in hope he causes us really to anticipate the fullness of communion with the Holy Trinity. Sent by the Father who hears the epiclesis of the Church, the Spirit gives life to those who accept him and is, even now, the "guarantee" of their inheritance.
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. 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.
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" 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.