Tertullian noted that the Passover provided a more than usually solemn day for baptisms, because it was the day when, in effect, the Lord’s Passion, into which we are baptised, was completed.
Justin martyr, writing in the second century, described the Eucharist thus: when the president had given thanks aand the congregation assented, the deacons gave to everyone present a portion of the consecrated bread and wine and water. No one was allowed to partake of the Eucharist except ‘one who believes that the things we teach are true, and has received the washing for forgiveness of sins and for rebirth, and who lives according to the way Christ handed down to us.’ He wrote further that:
we do not receive these things as common bread and common drink; but as Jesus Christ Our Saviour being Incarnate by God’s Word took flesh and blood for our salvation, so also we have been taught that the food consecrated by the words of prayer which comes from him, from which our flesh and blood are nourished by transformation, is the flesh and blood of that Incarnate Jesus
This was the teaching passed down by the Apostles, and it was what Christians had always done. This, Irenaeus also confirmed:
This is what the Church has received from the Apostles and throughout the world offers to God, who affords us nourishment as the first fruits of his gifts in the New Testament
Tertullian refutes the heresy of Marcion, who had taught that the bread was simply a symbol. It was Jesus who died for us, and he gives us his body. On Marcion’s theory it would not, Tertullian adds, have mattered if the bread had been crucified for us:
But in that case why would we need to call his body bread? Why not rather cone up with some more interesting edible thing, like a melon, which maybe Marcion had in place of a heart!
St John Damascene comments that as humans have a compound nature – body and spirit – it is appropriate that the new birth corresponds to that compound, and that the food of faith should, likewise, be compound. We were given a birth by water and the Spirit, that is, in holy baptism and then with the food of life which is Our Lord Jesus Christ, who, on the night he was betrayed, offered up a new covenant to his disciples and, through them, to all who believe in Him.
St Ambrose wrote that before the words of Christ, the chalice was full of wine, but when the words had been spoken, the blood in effect redeems the people:
So behold in what great respects the expression of Christ is able to change all things. Then the Lord Himself testified to us that we receive His body and blood. Should we doubt, at all, about his faith and testimony?
From the beginning until now, the holy sacrifice has been conducted in this way, and shall be until He shall come again to redeem the living and the dead, and to establish the kingdom which shall have no end.