But every Lord's day gather yourselves together, and break bread, and give thanksgiving after having confessed your transgressions, that your sacrifice may be pure. But let no one that is at variance with his fellow come together with you, until they be reconciled, that your sacrifice may not be profaned.
Now concerning the Thanksgiving (Eucharist), thus give thanks. First, concerning 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; to You be the glory forever.
Ignatius of Antioch · d. c. 110 AD · Epistle to the Philadelphians
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.
Ignatius of Antioch · d. c. 110 AD · Epistle to the Smyrnaeans
They stay away from the Eucharist and from prayer, because they will not confess that the Eucharist is the flesh of our Savior Jesus Christ. That flesh suffered for our sins. That flesh the Father in his kindness raised.
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.
1. The oblation of the Church, therefore, which the Lord gave instructions to be offered throughout all the world, is accounted with God a pure sacrifice, and is acceptable to Him;
But if this indeed do not attain salvation, then neither did the Lord redeem us with His blood, nor is the cup of the Eucharist the communion of His blood, nor the bread which we break the communion of His body.