Pope Saint Leo IX

“Without a doubt, it was for he alone whom the Lord and Savior asserted that he prayed that his faith would not fail, saying, ‘I have prayed for thee, etc.’ [Lk 22:32]. Such a venerable and efficacious prayer obtained that to this point the faith of Peter has not failed, nor can it be believed that it is ever going to fail in his throne.” (Pope Saint Leo IX (1049-54), Epistle to Peter of Antioch).


“By the See of the Chief of the Apostles, namely by the Roman Church, through the same Peter, as well as through his successors, have not the comments of all the heretics been disapproved, rejected, and overcome, and the hearts of the brethren in the faith of Peter — which so far neither has failed, nor up to the end will fail — been strengthened?” [In Terra Pax Hominibus; Denz. 351 [September 2, A.D. 1053]).


“… You are said to have condemned publicly in a strange presumption and incredible boldness the Apostolic and Latin Church, neither heard nor refuted, for the reason chiefly that it dared to celebrate the commemoration of the passion of the Lord from the Azymes. Behold your incautious reprehension, behold your evil boasting, when “you put your mouth into heaven. When your tongue passing on to the earth” [Ps. 72:9], by human arguments and conjectures attempts to uproot and overturn the ancient faith.…

“… The Holy Church built upon a Rock, that is Christ, and upon Peter or Cephas, the son of John who first was called Simon, because by the gates of Hell, that is, by the disputations of heretics which lead the vain to destruction, it would never be overcome; thus Truth itself promises, through whom are true, whatsoever things are true: “The gates of hell will not prevail against it” [Matt. 16:18]. The same Son declares that He obtained the effect of this promise from the Father by prayers, by saying to Peter: “Simon, behold Satan etc.” [Luke 23:31]. Therefore, will there be anyone so foolish as to dare to regard His prayer as in anyway vain whose being willing is being able? By the See of the chief of the Apostles, namely by the Roman Church, through the same Peter, as well as through his successors, have not the comments of all the heretics been disapproved, rejected, and overcome, and the hearts of the brethren in the faith of Peter which so far neither has failed, nor up to the end will fail, been strengthened?… By passing a preceding judgment on the great See, concerning which it is not permitted any man to pass judgment, you have received anathema from all the Fathers of all the venerable Councils… As the hinge while remaining immovable opens and closes the door, so Peter and his successors have free judgment over all the Church, since no one should remove their status because “the highest See is judged by no one.” (From the epistle “In terra pax hominibus” to Emperor Michael Cerularius and to Leo of Achrida, September 2, 1053 ; Denzinger, H., & Rahner, K. (Eds.). (1954). The sources of Catholic dogma. (R. J. Deferrari, Trans.) (p. 142). St. Louis, MO: B. Herder Book Co.).