The Church's faith precedes the faith of the believer who is invited to adhere to it. When the Church celebrates the sacraments, she confesses the faith received from the apostles - whence the ancient saying: lex orandi, lex credendi (or: legem credendi lex statuat supplicandi according to Prosper of Aquitaine [5th cent.]). The law of prayer is the law of faith: the Church believes as she prays. Liturgy is a constitutive element of the holy and living Tradition.
Source: Catechism of the Catholic Church (Vatican.va)