2nd Century
St. Ignatius of Antioch
Apostolic & Early Church
St. Ignatius of Antioch (c. 35 – c. 108), Bishop of Antioch and martyr, a disciple of the Apostle John. Wikipedia
"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. But it were better for them to treat it with respect, that they also might rise again. "
Letter to the Smyrnaeans 6:2–7:1
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Why this quote matters
Earliest post-apostolic witness against docetist heretics who denied Real Presence.
Source citation: Letter to the Smyrnaeans 6:2–7:1.