From the Catholic Encyclopedia (
newadvent.org/cathen/07790a.htm)
That the Church is infallible in her definitions on faith and morals is itself a Catholic dogma,
which, although it was formulated ecumenically for the first time in the Vatican Council, had been explicitly taught long before and had been assumed from the very beginning without question down to the time of the Protestant Reformation. …
Here is a link to the 1870 AD Vatican Council I documents from Session 4 dealing with the Papacy. Scroll down to Chapter 4. Here is paragraph 9 from that Chapter.
ewtn.com/library/councils/v1.htm#6
Vatican Council I (Session 4, Chapter 4, paragraph 9)
- Therefore, faithfully adhering to the tradition received from the beginning of the Christian faith, to the glory of God our savior, for the exaltation of the Catholic religion and for the salvation of the Christian people, with the approval of the Sacred Council, we teach and define as a divinely revealed dogma that when the Roman Pontiff speaks EX CATHEDRA, that is, when, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, he defines a doctrine concerning faith or morals to be held by the whole Church, he possesses, by the divine assistance promised to him in blessed Peter, that infallibility which the divine Redeemer willed his Church to enjoy in defining doctrine concerning faith or morals. Therefore, such definitions of the Roman Pontiff are of themselves, and not by the consent of the Church, irreformable.
Also the previous Chapter 2 which gives some earlier references.
2. So the fathers of the fourth Council of Constantinople, following the footsteps of their predecessors, published this solemn profession of faith: The first condition of salvation is to maintain the rule of the true faith. And since that saying of our lord Jesus Christ, You are Peter, and upon this rock I will build my Church [55], cannot fail of its effect, the words spoken are confirmed by their consequences. For in the Apostolic See the Catholic religion has always been preserved unblemished, and sacred doctrine been held in honor. Since it is our earnest desire to be in no way separated from this faith and doctrine, we hope that we may deserve to remain in that one communion which the Apostolic See preaches, for in it is the whole and true strength of the Christian religion [56].
What is more, with the approval of the second Council of Lyons, the Greeks made the following profession:
“The Holy Roman Church possesses the supreme and full primacy and principality over the whole Catholic Church. She truly and humbly acknowledges that she received this from the Lord himself in blessed Peter, the prince and chief of the apostles, whose successor the Roman Pontiff is, together with the fullness of power. And since before all others she has the duty of defending the truth of the faith, so if any questions arise concerning the faith, it is by her judgment that they must be settled.” [57]
Then there is the definition of the Council of Florence:
“The Roman Pontiff is the true vicar of Christ, the head of the whole Church and the father and teacher of all Christians; and to him was committed in blessed Peter, by our lord Jesus Christ, the full power of tending, ruling and governing the whole Church.” [58]