The liturgy daily builds up those who are within into a holy temple of the Lord, into a dwelling place for God in the Spirit, to the mature measure of the fullness of Christ, at the same time it marvelously strengthens their power to preach Christ and thus shows forth the Church to those who are outside as a sign lifted up among the nations, under which the scattered children of God may be gathered together, until there is one sheepfold and one shepherd. (SC 2)
The liturgy is the summit toward which the activity of the Church is directed; at the same time it is the fount from which all the Church’s power flows. (SC 10)
The vary nature of liturgical celebrations is to give the glory and praise to God through our full, conscious, and active participation. (SC 14)
Christ is always present in his Church, especially in its liturgical celebrations. He is present in the sacrifice of the Mass, not only in the person of his minister, "the same not offering, through the ministry of priests, who formerly offered himself on the cross," but especially under the eucharistic elements. 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." Mt 18:20 (SC 7)