Traditions of celibacy in the early Church

For as the husbandman throwing the seed into the ground awaits the harvest, not sowing more upon it, so to us the procreation of children is the measure of our indulgence in appetite. Nay, you would find many among us, both men and women, growing old unmarried, in hope of living in closer communion with God.

Athenagoras of Athens
A Plea for the Christians
Chapter XXXIII

Traditions of the Eucharist were handed down in secondary writings

Those who have become acquainted with the secondary (i.e., under Christ) constitutions of the apostles, are aware that the Lord instituted a new oblation in the new covenant, according to [the declaration of] Malachi the prophet.

…For we make an oblation to God of the bread and the cup of blessing, giving Him thanks in that He has commanded the earth to bring forth these fruits for our nourishment. And then, when we have perfected the oblation, we invoke the Holy Spirit, that He may exhibit this sacrifice, both the bread the body of Christ, and the cup the blood of Christ, in order that the receivers of these antitypes may obtain remission of sins and life eternal.

Irenaeus of Lyons
Lost Writings
Fragment XXXVII

Differences in fasting customs between East and West are accepted

Thus, in fact, the difference [in observing] the fast establishes the harmony of [our common] faith. For neither could Anicetus persuade Polycarp to forego the observance [in his own way], inasmuch as these things had been always [so] observed by John the disciple of our Lord, and by other apostles with whom he had been conversant; nor, on the other hand, could Polycarp succeed in persuading Anicetus to keep [the observance in his way], for he maintained that he was bound to adhere to the usage of the presbyters who preceded him.

…so that they parted in peace one from the other, maintaining peace with the whole Church, both those who did observe [this custom] and those who did not.

Irenaeus of Lyons
Lost Writings
Fragment III

The Church is the paradise of Eden

…but to flee to the Church, and be brought up in her bosom, and be nourished with the Lord’s Scriptures. For the Church has been planted as a garden (paradisus) in this world; therefore says the Spirit of God, “Thou mayest freely eat from every tree of the garden,” that is, Eat ye from every Scripture of the Lord; but ye shall not eat with an uplifted mind, nor touch any heretical discord.

Irenaeus of Lyons
Against Heresies, Book V
Chapter XX

The catholicity of the Church

But the path of those belonging to the Church circumscribes the whole world, as possessing the sure tradition from the apostles, and gives unto us to see that the faith of all is one and the same, since all receive one and the same God the Father, and believe in the same dispensation regarding the incarnation of the Son of God, and are cognizant of the same gift of the Spirit, and are conversant with the same commandments, and preserve the same form of ecclesiastical constitution, and expect the same advent of the Lord, and await the same salvation of the complete man, that is, of the soul and body.

…For the Church preaches the truth everywhere, and she is the seven-branched candlestick which bears the light of Christ.

Irenaeus of Lyons
Against Heresies, Book V
Chapter XX

Biblical interpretation must be done in light of catholic tradition

But here some one perhaps will ask, Since the canon of Scripture is complete, and sufficient of itself for everything, and more than sufficient, what need is there to join with it the authority of the Church’s interpretation? For this reason—because, owing to the depth of Holy Scripture, all do not accept it in one and the same sense, but one understands its words in one way, another in another; so that it seems to be capable of as many interpretations as there are interpreters. For Novatian expounds it one way, Sabellius another, Donatus another, Arius, Eunomius, Macedonius, another, Photinus, Apollinaris, Priscillian, another,Iovinian, Pelagius, Celestius, another, lastly, Nestorius another. Therefore, it is very necessary, on account of so great intricacies of such various error, that the rule for the right understanding of the prophets and apostles should be framed in accordance with the standard of Ecclesiastical and Catholic interpretation.

Moreover, in the Catholic Church itself, all possible care must be taken, that we hold that faith which has been believed everywhere, always, by all. For that is truly and in the strictest sense Catholic, which, as the name itself and the reason of the thing declare, comprehends all universally. This rule we shall observe if we follow universality, antiquity, consent. We shall follow universality if we confess that one faith to be true, which the whole Church throughout the world confesses; antiquity, if we in no wise depart from those interpretations which it is manifest were notoriously held by our holy ancestors and fathers; consent, in like manner, if in antiquity itself we adhere to the consentient definitions and determinations of all, or at the least of almost all priests and doctors.

St. Vincent of Lerins
Commonitory
Chapter 2:5-6

The OT prophets were also the body of Christ

For the prophets prefigured in themselves all these things, because of their love to God, and on account of His word. For since they themselves were members of Christ, each one of them in his place as a member did, in accordance with this, set forth the prophecy [assigned him]; all of them, although many, prefiguring only one, and proclaiming the things which pertain to one.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XXXIII

True doctrine is found through the succession of the ancient Church

True knowledge is [that which consists in] the doctrine of the apostles, and the ancient constitution of the Church throughout all the world, and the distinctive manifestation of the body of Christ according to the successions of the bishops, by which they have handed down that Church which exists in every place, and has come even unto us, being guarded and preserved without any forging of Scriptures, by a very complete system of doctrine, and neither receiving addition nor [suffering] curtailment [in the truths which she believes]; and [it consists in] reading [the word of God] without falsification, and a lawful and diligent exposition in harmony with the Scriptures, both without danger and without blasphemy; and [above all, it consists in] the pre-eminent gift of love, which is more precious than knowledge, more glorious than prophecy, and which excels all the other gifts [of God].

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XXXIII

 

No reformation of the Church through schism will ever make up for it’s mischief

He shall also judge those who give rise to schisms, who are destitute of the love of God, and who look to their own special advantage rather than to the unity of the Church; and who for trifling reasons, or any kind of reason which occurs to them, cut in pieces and divide the great and glorious body of Christ, and so far as in them lies, [positively] destroy it,—men who prate of peace while they give rise to war, and do in truth strain out a gnat, but swallow a camel. For no reformation of so great importance can be effected by them, as will compensate for the mischief arising from their schism. He shall also judge all those who are beyond the pale of the truth, that is, who are outside the Church; but he himself shall be judged by no one.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XXXIII

The Apostolic faith is through succession and is the key to the Scriptures

Where, therefore, the gifts of the Lord have been placed, there it behoves us to learn the truth, [namely,] from those who possess that succession of the Church which is from the apostles, and among whom exists that which is sound and blameless in conduct, as well as that which is unadulterated and incorrupt in speech. For these also preserve this faith of ours in one God who created all things; and they increase that love [which we have] for the Son of God, who accomplished such marvelous dispensations for our sake: and they expound the Scriptures to us without danger, neither blaspheming God, nor dishonoring the patriarchs, nor despising the prophets.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XXVII