ca. 96 A.D., Pope Saint Clement, fourth Bishop of Rome, disciple of the Apostles Peter and Paul, Letter to the Corinthians
58:2 Accept our counsel [i.e., the counsel of the Church of Rome] and you will have nothing to regret. For as God lives, and as the Lord Jesus Christ lives, and the Holy Spirit, and the faith and hope of the elect, as surely will he that humbly and with equanimity and without regret carries out the commandments and precepts given by God, be enrolled and chosen among the number of those who are being saved through Jesus Christ, through whom there is glory to Him forever and ever. Amen. …
59:1 If anyone disobey the things which have been said by Him [i.e., God] through us [i.e., the Church of Rome], let them know that they will involve themselves in transgression and in no small danger. …
63:2 You will afford us joy and gladness if, being obedient to the things which we have written through the Holy Spirit, you will root out the wicked passion of jealousy, in accord with the plea for peace and concord which we have made in this letter.
— ca. 100 A.D., Death of Saint John, the last of the Apostles —
ca. 107 A.D., Saint Ignatius, Bishop of Antioch, Disciple of the Apostle John, Letter to the Smyrneans
— Earliest extant use of the title "Catholic Church" —
8:1 You must all follow the bishop as Jesus Christ follows the Father, and the presbytery as you would the Apostles. Reverence the deacons as you would the command of God. Let no one do anything of concern to the Church without the bishop. Let that be considered a valid Eucharist which is celebrated by the bishop, or by one to whom he appoints. 2 Wherever the bishop appears, let the people be there; just as wherever Jesus Christ is, there is the Catholic Church.
The Martyrdom of Saint Polycarp, ca. 156 A.D.: The Church of God which sojourns in Smyrna, to the Church of God which sojourns in Philomelium, and to all the dioceses of the holy and Catholic Church in every place: May mercy, peace, and love of God the Father and of our Lord Jesus Christ be given you in abundance (Jude 1:2).
ca. 185 A.D. — Saint Irenaeus, Bishop of Lyons, disciple of Saint Polycarp of Smyrna, Against Heresies
1:10:2 As I said before, the Church, having received this preaching and this faith, although she is disseminated throughout the whole world, yet guarded it, as if she occupied but one house. She likewise believes these things just as if she had but one soul and one and the same heart; and harmoniously she proclaims them and teaches them and hands them down, as if she possessed but one mouth. For, while the languages of the world are diverse, nevertheless, the authority of the tradition is one and the same.
Neither do the Churches among the Germans believe otherwise or have another tradition, nor do those among the Iberians, nor among the Celts, nor away in the East, nor in Egypt, nor in Libya, nor those which have been established in the central regions of the world. But just as the sun, that creature of God, is one and the same throughout the whole world, so also the preaching of the truth shines everywhere and enlightens all men who desire to come to a knowledge of truth. …
Nor will any of the rulers in the Churches, whatever his power of eloquence, teach otherwise, for no one is above the teacher (Matt. 10:24; Luke 6:40); nor will he who is weak in speaking detract from the tradition. For the faith is one and the same, and cannot be amplified by one who is able to say much about it, nor can it be diminished by one who can say but little. …
3:3:1 It is possible, then, for everyone in every Church, who may wish to know the truth, to contemplate the tradition of the Apostles which has been made known throughout the whole world. And we are in a position to enumerate those who were instituted bishops by the Apostles, and their successors to our own times: men who neither knew nor taught anything like these heretics rave about. …
3:3:2 But since it would be too long to enumerate in such a volume as this the successions of all the Churches, we shall confound all those who, in whatever manner, whether through self-satisfaction or vainglory, or through blindness and wicked opinion, assemble other than where it is proper, by pointing out here the successions of the bishops of the greatest and most ancient Church known to all, founded and organized at Rome by the two most glorious Apostles, Peter and Paul, that Church which has the tradition and the faith which comes down to us after having been announced to men by the Apostles. For with this Church, because of its superior origin, all Churches must agree, that is, all the faithful in the whole world; and it is in her that the faithful everywhere have maintained the Apostolic tradition. …
3:4:1 When, therefore, we have such proofs, it is not necessary to seek among others the truth which is easily obtained from the Church. For the Apostles, like a rich man in a bank, deposited with her most copiously everything which pertains to the truth; and everyone whosoever wishes draws from her the drink of life (Rev. 22:17). For she is the entrance to life, while all the rest are thieves and robbers. That is why it is surely necessary to avoid them, while cherishing with the utmost diligence the things pertaining to the Church, and to lay hold of the tradition of truth. What then? If there should be a dispute over some kind of question, ought we not have recourse to the most ancient Churches in which the Apostles were familiar, and draw from them what is clear and certain in regard to that question? What if the Apostles had not in fact left writings to us? Would it not be necessary to follow the order of tradition, which was handed down to those to whom they entrusted the Churches? …
3:24:1 The preaching of the Church truly continues without change and is everywhere the same, and has the testimony of the Prophets and the Apostles and all their disciples. … In the Church, God has placed apostles, prophets and doctors, and all the other means through which the Spirit works (1 Cor. 12:28); in all of which none have any part who do not conform to the Church. … For where the Church is, there is the Spirit of God; and where the Spirit of God, there the Church and every grace. The Spirit, however, is Truth. …
4:26:2 It is necessary to obey those who are the presbyters in the Church, those who, as we have shown, have succession from the Apostles; those who have received, with the succession of the episcopate, the sure charism of truth [i.e., the gift of infallibility] according to the good pleasure of the Father. But the rest, who have no part in the primitive succession and assemble wheresoever they will, must be held in suspicion.
ca. 190 A.D., Saint Abercius Marcellus, Bishop of Hieropolis, Epitaph
[The chaste shepherd (i.e., Jesus Christ)] taught me the faithful writings in life.
He sent me to Rome to contemplate a kingdom,
And to behold a queen in a golden robe and golden sandals [i.e., the Church].
There I saw a people who had the resplendent seal [i.e., Baptism].
ca. 200 A.D., Tertullian, The Demurrer Against the Heretics
21:1-7 From this, therefore, do we draw up our rule. Since the Lord Jesus Christ sent the apostles to preach, (our rule is) that no others ought to be received as preachers than those whom Christ appointed; for “no man knoweth the Father save the Son, and he to whomsoever the Son will reveal Him” (Mt. 11:27). Nor does the Son seem to have revealed Him to any other than the apostles, whom He sent forth to preach—that, of course, which He revealed to them. Now, what that was which they preached—in other words, what it was which Christ revealed to them—can, as I must here likewise prescribe, properly be proved in no other way than by those very churches which the apostles founded in person, by declaring the gospel to them directly themselves, both viva voce, as the phrase is, and subsequently by their epistles. If, then, these things are so, it is in the same degree manifest that all doctrine which agrees with the apostolic churches—those moulds and original sources of the faith must be reckoned for truth, as undoubtedly containing that which the (said) churches received from the apostles, the apostles from Christ, Christ from God. It remains, then, that we demonstrate whether this doctrine of ours, of which we have now given the rule, has its origin in the tradition of the apostles, and whether all other doctrines do not ipso facto proceed from falsehood. We hold communion with the apostolic churches because our doctrine is in no respect different from theirs. This is our witness of truth. …
28:1 Grant, then, that all have erred; that the apostle was mistaken in giving his testimony; that the Holy Ghost had no such respect to any one (church) as to lead it into truth, although sent with this view by Christ (cf. Jn. 14:26), and for this asked of the Father that He might be the teacher of truth (cf. Jn. 15:26); grant, also, that He, the Steward of God, the Vicar of Christ [i.e., the Holy Spirit], neglected His office, permitting the churches for a time to understand differently, (and) to believe differently, what He Himself was preaching by the apostles,—is it likely that so many churches, and they so great, should have gone astray into one and the same faith? …
32:1-4 [I]f there be any (heresies) which are bold enough to plant themselves in the midst of the apostolic age, that they may thereby seem to have been handed down by the apostles, because they existed in the time of the apostles, we can say: Let them produce the original records of their churches; let them unfold the roll of their bishops, running down in due succession from the beginning in such a manner that [that first bishop of theirs] bishop shall be able to show for his ordainer and predecessor some one of the apostles or of apostolic men,—a man, moreover, who continued steadfast with the apostles. For this is the manner in which the apostolic churches transmit their registers: as the church of Smyrna, which records that Polycarp was placed therein by John; as also the church of Rome, which makes Clement to have been ordained in like manner by Peter. In exactly the same way the other churches likewise exhibit (their several worthies), whom, as having been appointed to their episcopal places by apostles, they regard as transmitters of the apostolic seed. Let the heretics contrive something of the same kind. …
37:1-2 Since this is the case, in order that the truth may be adjudged to belong to us, “as many as walk according to the rule,” which the church has handed down from the apostles, the apostles from Christ, and Christ from God, the reason of our position is clear, when it determines that heretics ought not to be allowed to challenge an appeal to the Scriptures, since we, without the Scriptures, prove that they have nothing to do with the Scriptures.
ca. 203 A.D., Saint Clement of Alexandria, The Instructor of the Children
1:6:42:1 When the loving and benevolent Father had rained down the Word, that Word then became the spiritual nourishment of those who have good sense. O mystic wonder! The Father of all is indeed one, one also is the universal Word, and the Holy Spirit is one and the same everywhere; and one is the Virgin Mother. I love to call her the Church. This Mother alone was without milk, because she alone did not become a wife. She is at once both Virgin and Mother: as a Virgin, undefiled; as a Mother full of love.