From the first apology in defense of the Christians by Saint Justin, martyr (Cap. 66-67: PB 6, 427-431)
The celebration of the eucharist
No one may share the eucharist with us unless he believes that what we teach is true, unless he is washed in the regenerating waters of baptism for the remission of his sins, and unless he lives in accordance with the principles given us by Christ.
We do not consume the eucharistic bread and wine as if it were ordinary food and drink, for we have been taught that as Jesus Christ our Savior became a man of flesh and blood by the power of the Word of God, so also the food that our flesh and blood assimilates for its nourishment becomes the flesh and blood of the incarnate Jesus by the power of his own words contained in the prayer of thanksgiving.
The apostles, in their recollections, which are called gospels, handed down to us what Jesus commanded them to do. They tell us that he took bread, gave thanks and said: Do this in memory of me. This is my body. In the same way he took the cup, he gave thanks and said: This is my blood. The Lord gave this command to them alone. Ever since then we have constantly reminded one another of these things. The rich among us help the poor and we are always united. For all that we receive we praise the Creator of the universe through his Son Jesus Christ and through the Holy Spirit.
On Sunday we have a common assembly of all our members, whether they live in the city or the outlying districts. The recollections of the apostles or the writings of the prophets are read, as long as there is time. When the reader has finished, the president of the assembly speaks to us; he urges everyone to imitate the examples of virtue we have heard in the readings. Then we all stand up together and pray.
On the conclusion of our prayer, bread and wine and water are brought forward. The president offers prayers and gives thanks to the best of his ability, and the people give assent by saying, “Amen.” The eucharist is distributed, everyone present communicates, and the deacons take it to those who are absent.
The wealthy, if they wish, may make a contribution, and they themselves decide the amount. The collection is placed in the custody of the president, who uses it to help the orphans and widows and all who for any reason are in distress, whether because they are sick, in prison, or away from home. In a word, he takes care of all who are in need.
We hold our common assembly on Sunday because it is the first day of the week, the day on which God put darkness and chaos to flight and created the world, and because on that same day our savior Jesus Christ rose from the dead. For he was crucified on Friday and on Sunday he appeared to his apostles and disciples and taught them the things that we have passed on for your consideration.
From a sermon by Saint Augustine, bishop (Sermo 8 in octava Paschae 1, 4: PL 46, 838. 841)
A new creation in Christ
I speak to you who have just been reborn in baptism, my little children in Christ, you who are the new offspring of the Church, gift of the Father, proof of Mother Church’s fruitfulness. All of you who stand fast in the Lord are a holy seed, a new colony of bees, the very flower of our ministry and fruit of our toil, my joy and my crown. It is the words of the Apostle that I address to you: Put on the Lord Jesus Christ, and make no provision for the flesh and its desires, so that you may be clothed with the life of him whom you have put on in this sacrament. You have all been clothed with Christ by your baptism in him. There is neither Jew nor Greek; there is neither slave nor freeman; there is neither male nor female; you are all one in Christ Jesus.
Such is the power of this sacrament: it is a sacrament of new life which begins here and now with the forgiveness of all past sins, and will be brought to completion in the resurrection of the dead. You have been buried with Christ by baptism into death in order that, as Christ has risen from the dead, you also may walk in newness of life.
You are walking now by faith, still on pilgrimage in a mortal body away from the Lord; but he to whom your steps are directed is himself the sure and certain way for you: Jesus Christ, who for our sake became man. For all who fear him he has stored up abundant happiness, which he will reveal to those who hope in him, bringing it to completion when we have attained the reality which even now we possess in hope.
This is the octave day of your new birth. Today is fulfilled in you the sign of faith that was prefigured in the Old Testament by the circumcision of the flesh on the eighth day after birth. When the Lord rose from the dead, he put off the mortality of the flesh; his risen body was still the same body, but it was no longer subject to death. By his resurrection he consecrated Sunday, or the Lord’s day. Though the third after his passion, this day is the eighth after the Sabbath, and thus also the first day of the week.
And so your own hope of resurrection, though not yet realized, is sure and certain, because you have received the sacrament or sign of this reality, and have been given the pledge of the Spirit. If, then, you have risen with Christ, seek the things that are above, where Christ is seated at the right hand of God. Set your hearts on heavenly things, not the things that are on earth. For you have died and your life is hidden with Christ in God. When Christ, your life, appears, then you too will appear with him in glory.