Recommended Book: Pope Leo XIV: Inside the Conclave and the Dawn of a New Papacy (paid link)

We, continuing in the regal path, and following the divinely inspired teaching of the Holy Fathers, and the tradition of the Catholic Church . . . For thus the doctrine of our Holy Fathers, that is, the tradition of the Catholic Church which has received the Gospel from and even to the end of the world is strengthened. Thus we follow Paul, who spoke in Christ (2 Cor 2:17), and all the divine apostolic group and the paternal sanctity keeping the traditions (2 Thess 2:15) which we have received.

Council of Nicea II [A.D. 787]