Pope Clement I:
If, however, any shall disobey the words spoken by Him through us, let them know that they will involve themselves in transgression and serious danger.
Joy and gladness will you afford us, if you become obedient to the words written by us and through the Holy Spirit root out the lawless wrath of your jealousy according to the intercession which we have made for peace and unity in this letter.
Saint Irenaeus of Lyon:
Since, however, it would be very tedious, in such a volume as this, to reckon up the successions of all the Churches, we do put to confusion all those who, in whatever manner, whether by an evil self-pleasing, by vainglory, or by blindness and perverse opinion, assemble in unauthorized meetings; by indicating that tradition derived from the apostles, of the very great, the very ancient, and universally known Church founded and organized at Rome by the two most glorious apostles, Peter and Paul; as also the faith preached to men, which comes down to our time by means of the successions of the bishops. For it is a matter of necessity that every Church should agree with this Church, on account of its preeminent authority, that is, the faithful everywhere, inasmuch as the tradition has been preserved continuously by those who exist everywhere.
Saint Cyprian of Carthage:
After such things as these, moreover, they still dare— a false bishop having been appointed for them by, heretics— to set sail and to bear letters from schismatic and profane persons to the throne of Peter, and to the chief church whence priestly unity takes its source; and not to consider that these were the Romans whose faith was praised in the preaching of the apostle, to whom faithlessness could have no access.
The Formula of Hormisdas:
For it is impossible that the words of our Lord Jesus Christ, who said, "Thou art Peter, and upon this rock I will build my Church," should not be verified. And their truth has been proved by the course of history, for in the Apostolic See the Catholic religion has always been kept unsullied.
Following, as we have said before, the Apostolic See in all things and proclaiming all its decisions, we endorse and approve all the letters which Pope St Leo wrote concerning the Christian religion. And so I hope I may deserve to be associated with you in the one communion which the Apostolic See proclaims, in which the whole, true, and perfect security of the Christian religion resides. I promise that from now on those who are separated from the communion of the Catholic Church, that is, who are not in agreement with the Apostolic See, will not have their names read during the sacred mysteries. But if I attempt even the least deviation from my profession, I admit that, according to my own declaration, I am an accomplice to those whom I have condemned. I have signed this, my profession, with my own hand, and I have directed it to you, Hormisdas, the holy and venerable pope of Rome.
The Sixth Ecumenical Council:
For this is the rule of the true faith, which this spiritual mother of your most tranquil empire, the Apostolic Church of Christ, has both in prosperity and in adversity always held and defended with energy; which, it will be proved, by the grace of Almighty God, has never erred from the path of the apostolic tradition, nor has she been depraved by yielding to heretical innovations, but from the beginning she has received the Christian faith from her founders, the princes of the Apostles of Christ, and remains undefiled unto the end, according to the divine promise of the Lord and Saviour himself, which he uttered in the holy Gospels to the prince of his disciples: saying, Peter, Peter, behold, Satan has desired to have you, that he might sift you as wheat; but I have prayed for you, that (your) faith fail not. And when you are converted, strengthen your brethren. Let your tranquil Clemency therefore consider, since it is the Lord and Saviour of all, whose faith it is, that promised that Peter's faith should not fail and exhorted him to strengthen his brethren, how it is known to all that the Apostolic pontiffs, the predecessors of my littleness, have always confidently done this very thing: of whom also our littleness, since I have received this ministry by divine designation, wishes to be the follower, although unequal to them and the least of all.
The Seventh Ecumenical Council:
And especially if you follow the tradition of the orthodox Faith of the Church of the holy Peter and Paul, the chief Apostles, and embrace their Vicar, as the Emperors who reigned before you of old both honoured their Vicar, and loved him with all their heart: and if your sacred majesty honour the most holy Roman Church of the chief Apostles, to whom was given power by God the Word himself to loose and to bind sins in heaven and earth. For they will extend their shield over your power, and all barbarous nations shall be put under your feet: and wherever you go they will make you conquerors. For the holy and chief Apostles themselves, who set up the Catholic and orthodox Faith, have laid it down as a written law that all who after them are to be successors of their seats, should hold their Faith and remain in it to the end.
The Eighth Ecumenical Council:
We believe that the saying of the Lord that Christ addressed to his holy apostles and disciples, "Whoever receives you receives me, and whoever despises you despises me," was also addressed to all who were likewise made supreme pontiffs and chief pastors in succession to them in the catholic church.