On the eucharist
St Ignatious of antioch diciple of John, Epistle to the Philadelphians
Chapter 4. Have but one Eucharist,
Take heed, then, to have but one Eucharist. For there is one flesh of our Lord Jesus Christ, and one cup to [show forth] the unity of His blood; one altar; as there is one bishop, along with the presbytery and deacons, my fellow-servants: that so, whatsoever you do, you may do it according to [the will of] God.
The Epistle of Ignatius to the Smyrnaeans
Chapter 7. Let us stand aloof from such heretics.
They abstain from the Eucharist and from prayer, because they confess not the Eucharist to be the flesh of our Saviour Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again. Those, therefore, who speak against this gift of God, incur death in the midst of their disputes.
St Justin Martyr The First Apology
Chapter 66. Of the Eucharist.
And this food is called among us Εὐχαριστία [the Eucharist], of which no one is allowed to partake but the man who believes that the things which we teach are true, and who has been washed with the washing that is for the remission of sins, and unto regeneration, and who is so living as Christ has enjoined. For not as common bread and common drink do we receive these; but in like manner as Jesus Christ our Saviour, having been made flesh by the Word of God, had both flesh and blood for our salvation, so likewise have we been taught that the food which is blessed by the prayer of His word, and from which our blood and flesh by transmutation are nourished, is the flesh and blood of that Jesus who was made flesh. For the apostles, in the memoirs composed by them, which are called Gospels, have thus delivered unto us what was enjoined upon them; that Jesus took bread, and when He had given thanks, said, “This do in remembrance of Me, Luke 22:19 this is My body;” and that, after the same manner, having taken the cup and given thanks, He said, “This is My blood;” and gave it to them alone. Which the wicked devils have imitated in the mysteries of Mithras, commanding the same thing to be done. For, that bread and a cup of water are placed with certain incantations in the mystic rites of one who is being initiated, you either know or can learn.
St Cyril bishop of Jerusalem On the Body and Blood of Christ.
on the priesthood
The Epistle of Ignatius to the Smyrnaeans
Chapter 8. Let nothing be done without the bishop.
See that you all follow the bishop, even as Jesus Christ does the Father, and the presbytery as you would the apostles; and reverence the deacons, as being the institution of God. Let no man do anything connected with the Church without the bishop. Let that be deemed a proper Eucharist, which is [administered] either by the bishop, or by one to whom he has entrusted it. Wherever the bishop shall appear, there let the multitude [of the people] also be; even as, wherever Jesus Christ is, there is the Catholic Church. It is not lawful without the bishop either to baptize or to celebrate a love-feast; but whatsoever he shall approve of, that is also pleasing to God, so that everything that is done may be secure and valid.
Chapter 9. Honour the bishop.
Moreover, it is in accordance with reason that we should return to soberness [of conduct], and, while yet we have opportunity, exercise repentance towards God. It is well to reverence both God and the bishop. He who honours the bishop has been honoured by God; he who does anything without the knowledge of the bishop, does [in reality] serve the devil. Let all things, then, abound to you through grace, for you are worthy. You have refreshed me in all things, and Jesus Christ [shall refresh] you. You have loved me when absent as well as when present. May God recompense you, for whose sake, while you endure all things, you shall attain unto Him.
On the perpetual virginity of Mary
The Perpetual Virginity of Blessed Mary by St Jerome