“The church of God which sojourns at Rome to the church of God which sojourns at Corinth … But if any disobey the words spoken by him through us, let them know that they will involve themselves in transgression and in no small danger.” Clement of Rome, Pope, 1st Epistle to the Corinthians, 1,59:1 (c. A.D. 96).
“Ignatius, who is also called Theophorus, to the Church which has obtained mercy, through the majesty of the Most High God the Father, and of Jesus Christ, His only-begotten Son; the Church which is sanctified and enlightened by the will of God, who formed all things that are according to the faith and love of Jesus Christ, our God and Saviour; the Church which presides in the place of the region of the Romans, and which is worthy of God, worthy of honour, worthy of the highest happiness, worthy of praise, worthy of credit, worthy of being deemed holy, and which presides over love…” Ignatius of Antioch, Epistle to the Romans, Prologue (A.D. 110).
"There is extant also another epistle written by Dionysius to the Romans, and addressed to Soter, who was bishop at that time. We cannot do better than to subjoin some passages from this epistle…In this same epistle he makes mention also of Clement’s epistle to the Corinthians, showing that it had been the custom from the beginning to read it in the church. His words are as follows: To-day we have passed the Lord’s holy day, in which we have read your epistle. From it, whenever we read it, we shall always be able to draw advice, as also from the former epistle, which was written to us through Clement.’ Dionysius of Corinth, To Pope Soter (A.D. 171).
“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; [we do this, I say,] 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 [by pointing out] 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 pre- eminent authority, that is, the faithful everywhere, inasmuch as the apostolical tradition has been preserved continuously by those [faithful men] who exist everywhere.” Irenaeus, Against Heresies, 3:3:2 (A.D. 180).
Primacy of Peter’s Apostolic See
“A question of no small importance arose at that time. For the parishes of all Asia, as from an older tradition, held that the fourteenth day of the moon, on which day the Jews were commanded to sacrifice the lamb, should be observed as the feast of the Saviour’s Passover. It was therefore necessary to end their fast on that day, whatever day of the week it should happen to be. But it was not the custom of the churches in the rest of the world to end it at this time, as they observed the practice which, from apostolic tradition, has prevailed to the present time, of terminating the fast on no other day than on that of the resurrection of our Saviour…Thereupon Victor, who presided over the church at Rome, immediately attempted to cut off from the common unity the parishes of all Asia, with the churches that agreed with them, as heterodox; and he wrote letters and declared all the brethren there wholly excommunicated.”(Eusebius Pamphilius-Pope Victor & Easter (c. A.D. 195))
CYPRIAN:
With a false bishop appointed for themselves by heretics, they dare even to set sail and carry letters from schismatics and blasphemers to the Chair of Peter and to the principal church [at Rome], in which sacerdotal unity has its source" (Epistle to Cornelius [Bishop of Rome] 59:14 [A.D. 252]).