The DidacheTeaches: The church's thanksgiving is a pure sacrifice
c. 100 AD · Didache 14
On the Lord's day, gather together, break bread, and give thanks, after you have confessed your transgressions, so that your sacrifice may be pure. Anyone who has a dispute with his companion must not join you until they are reconciled, so that your sacrifice may not be defiled.
The DidacheTeaches: The church's thanksgiving is a pure sacrifice
c. 100 AD · Didache 9
Now concerning the Eucharist, give thanks in this way. First, over the cup: “We thank you, our Father, for the holy vine of David your servant, which you made known to us through Jesus your servant. Yours is the glory forever.”
Make every effort, then, to share in one Eucharist. For there is one flesh of our Lord Jesus Christ and one cup that unites us in his blood, one altar, just as there is one bishop together with the council of elders and the deacons, my fellow servants. Do this so that whatever you do, you may act according to God.
They abstain from the Eucharist and from prayer, because they do not confess that the Eucharist is the flesh of our Savior Jesus Christ, the flesh that suffered for our sins and that the Father raised up in his goodness. So those who speak against the gift of God die in their disputing.
Justin MartyrTeaches: The Eucharist is the flesh and blood of Christ
c. 100–c. 165 AD · First Apology 66
We call this food the Eucharist, and no one may share in it except the person who believes that what we teach is true, who has been washed in the bath for the forgiveness of sins and for rebirth, and who lives as Christ handed down. For we do not receive these as common bread or common drink.
Irenaeus of LyonsTeaches: The church's thanksgiving is a pure sacrifice
c. 130–c. 202 AD · Against Heresies 4.18
The Church's offering, which the Lord commanded to be offered throughout the world, is regarded as a pure sacrifice before God and is accepted by Him; God does not need a sacrifice from us, but the one who offers is glorified in the very act of offering, provided his gift is accepted.
Irenaeus of LyonsTeaches: The Eucharist is the flesh and blood of Christ
c. 130–c. 202 AD · Against Heresies 5.2.2-3
Those who claim that God came into something alien, as if desiring what is foreign, are empty in their thinking. They suppose He did this to present a man made by another to a God who neither made nor founded anything, a man abandoned from the beginning by the true fashioning of humanity.