Catechism of the Catholic Church
1153 A sacramental celebration is a meeting of God's children with their Father, in Christ and the Holy Spirit; this meeting takes the form of a dialogue, through actions and words. Admittedly, the symbolic actions are already a language, but the Word of God and the response of faith have to accompany and give life to them, so that the seed of the Kingdom can bear its fruit in good soil. The liturgical actions signify what the Word of God expresses: both his free initiative and his people's response of faith.
1154 The liturgy of the Word is an integral part of sacramental celebrations. To nourish the faith of believers, the signs which accompany the Word of God should be emphasized: the book of the Word (a lectionary or a book of the Gospels), its veneration (procession, incense, candles), the place of its proclamation (lectern or ambo), its audible and intelligible reading, the minister's homily which extends its proclamation, and the responses of the assembly (acclamations, meditation psalms, litanies, and profession of faith).
1155 The liturgical word and action are inseparable both insofar as they are signs and instruction and insofar as they accomplish what they signify. When the Holy Spirit awakens faith, he not only gives an understanding of the Word of God, but through the sacraments also makes present the "wonders" of God which it proclaims. The Spirit makes present and communicates the Father's work, fulfilled by the beloved Son.
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.