Ignatius of Antioch — Epistle to the Smyrnaeans (Chapter 7. Let us stand aloof from such heretics)
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. Those who argue against God's gift die arguing. They would do better to love, so that they too might rise.
So it is right to stay clear of such people and not talk about them, privately or publicly. Give your attention to the prophets, and above all to the gospel. There the passion has been shown to us, and the resurrection made complete. Run from divisions. They are where evil begins.
Greek
Εὐχαριστίας καὶ πρυσευχῆς ἀπέχονται, διὰ τὸ μὴ ὁμολογεῖν τὴν εὐχαριστίαν σάρκα εἶναι τοῦ σωτῆρος ἡμῶν Ἰησοῦ Χριστοῦ τὴν ὑπὲρ τῶν ἁμαρτιῶν ἡμῶν παθοῦσαν, ἣν τῇ χρηστότητι ὁ πατὴρ ἤγειρεν. οἱ οὖν ἀντιλέγοντες τῇ δωρεᾷ τοῦ θεοῦ συζητοῦντες ἀποθνήσκουσιν: συνέφερεν δε αὐτοῖς ἀγαπᾶν, ἵνα καὶ ἀναστῶσιν.
πρέπον ἐστὶν ἀπέχεσθαι τῶν τοιούτων καὶ μήτε κατ’ ἰδίαν περὶ αὐτῶν λαλεῖν μήτε κοινῇ, προσέχειν δὲ τοῖς προφήταις, ἐξαιρέτως δὲ τῷ εὐαγγελίῳ, ἐν ᾧ τὸ πάθος ἡμῖν δεδήλωται καὶ ἡ ἀνάστασις τετελείωται. τοὺς δὲ μερισμοὺς φεύγετε ὡς ἀρχὴν κακῶν.