The deposit of faith (depositum fidei) is the body of revealed truth in the Scriptures and Tradition proposed by the Roman Catholic Church for the belief of the faithful. The phrase has a similar use in the US Episcopal Church.
The "sacred deposit" of the faith (depositum fidei) refers to the teachings of the Catholic Church that are believed to be handed down since the time of the Apostles - namely scripture and sacred tradition. St. Paul uses the Greek word paratheke ("deposit") meaning something precious entrusted to a depositary for safekeeping, when he says, in 1 Timothy 6:20 "O Timothy, guard what has been entrusted to you."; and again in 2 Timothy 1:14 "Guard this rich trust with the help of the holy Spirit that dwells within us." The concept of a priceless divine deposit entrusted to the teaching Church is one of the themes found in the New Testament.
"Sacred tradition and Sacred Scripture form one sacred deposit of the word of God, committed to the Church." "They flow out of the same divine wellspring and together make up one sacred deposit of faith from which the Church derives her certainty about revelation."
They are interpreted and transmitted through the Magisterium, the teaching authority of the Church, which is entrusted to the Pope and to the bishops in communion with him. On the occasion of the publication of the new catechism, following the Second Vatican Council, Pope John Paul II issued the Apostolic Constitution Fidei Depositum, in which he said, "Guarding the deposit of faith is the mission which the Lord has entrusted to his Church and which she fulfils in every age." Divine Revelation ended with the death of the last apostle, St. John. The development of doctrine does not add to Revelation, nor increase the Deposit of Faith but increases understanding of it. "Even if the Revelation is already complete, it has not been made fully explicit; it remains for Christian faith gradually to grasp its full significance over the course of the centuries".
In the Episcopal Church, the "deposit of faith" refers to "[t]he saving revelation of Christ that has been given to the church, especially as known through biblical witness and tradition". St. Paul speaks of tradition (1 Corinthians 11:2), both apostolic tradition and the traditions of men. In Colossians 2:8, he warns about the latter.
Unlike the Catholic Church which sees scripture and tradition as two complementary forms of revelation, the Anglican Church sees Apostolic tradition as including the holy scriptures, the ancient creeds, the dogmatic teachings of the seven ecumenical councils, the consensus of the Fathers of the Church, the Liturgy of the Church, and even the canons and artwork of the Church.
Vincent of Lerins stated that the canon of Scripture is complete, but to it must be joined the interpretation of the Church. "[W]e ought, with the Lord's help, to fortify our faith in a two-fold manner, firstly, that is, by the authority of God's Law [Scripture], then by the tradition of the Catholic Church." The Church is "a witness and a keeper of Holy Writ," interpreted according to apostolic tradition. In "A Treatise of the Sabbath day", Francis White, Bishop of Ely, wrote "Genuine Traditions agreeable to the Rule of Faith, subservient to piety, consonant with Holy Scripture, derived from Apostolical times by a successive current, and which have the uniform testimony of pious Antiquity, are received and honoured by us."