45 In the celebration of the sacraments, the Church hands down her memory especially through the profession of faith. The creed does not only involve giving one’s assent to a body of abstract truths; rather, when it is recited the whole of life is drawn into a journey towards full communion with the living God. We can say that in the creed believers are invited to enter into the mystery which they profess and to be transformed by it. To understand what this means, let us look first at the contents of the creed. It has a trinitarian structure: the Father and the Son are united in the Spirit of love. The believer thus states that the core of all being, the inmost secret of all reality, is the divine communion. The creed also contains a christological confession: it takes us through all the mysteries of Christ’s life up to his death, resurrection and ascension into heaven before his final return in glory. It tells us that this God of communion, reciprocal love between the Father and the Son in the Spirit, is capable of embracing all of human history and drawing it into the dynamic unity of the Godhead, which has its source and fulfillment in the Father. The believer who professes his or her faith is taken up, as it were, into the truth being professed. He or she cannot truthfully recite the words of the creed without being changed, without becoming part of that history of love which embraces us and expands our being, making it part of a great fellowship, the ultimate subject which recites the creed, namely, the Church. All the truths in which we believe point to the mystery of the new life of faith as a journey of communion with the living God.
Source: Lumen Fidei (Vatican.va)