Ignatius of Antioch, Epistle to the Philadelphians 2
You are children of the light of truth (Ephesians 5:8), so run from division and from evil teaching. Wherever the shepherd is, be there, following like sheep. Many wolves wear a trustworthy face, and with wicked pleasure they carry off as captives those who are running toward God. But in your unity they will have no room.
Greek
Τέκνα οὖν φωτὸς ἀληθείας, φεύγετε τὸν μερισμὸν καὶ τὰς κακοδιδασκαλίας: ὅπου δὲ ὁ ποιμήν ἐστιν, ἐκεῖ ὡς πρόβατα ἀκολουθεῖτε.
πολλοὶ γὰρ λύκοι ἀξιόπιστοι ἡδονῇ κακῇ αἰχμαλωτίζουσιν τοὺς θεοδρόμους: ἀλλ’ ἐν τῇ ἑνότητι ὑμῶν οὐχ ἕξουσιν τόπον.