Ignatius of Antioch, Epistle to the Trallians 6
So I urge you, or rather not I, but the love of Jesus Christ urges you: eat only Christian food, and keep clear of every foreign plant. That plant is heresy.
Such people blend Jesus Christ in with themselves, putting on a show of trustworthiness. They are like poisoners who serve a deadly drug in sweet wine. The one who does not know drinks it down with pleasure, and with that evil pleasure swallows his own death.
Greek
Παρακαλῶ οὖν ὑμᾶς, οὐκ ἐγώ, ἀλλ’ ἡ ἀγάπη Ἰησοῦ Χριστοῦ: μόνῃ τῇ χριστιανῇ τροφῇ χρῆσθε, ἀλλοτρίας δὲ βοτάνης ἀπέχεσθε, ἥτις ἐστὶν αἵρεσις:
οἳ ἑαυτοῖς παρεμπλέκουσιν Ἰησοῦν Χριστὸν καταξιοπιστευόμενοι, ὥσπερ θανάσιμον φάρμακον διδόντες μετὰ οἰνομέλιτος, ὅπερ ὁ ἀγνοῶν ἡδέως λαμβάνει ἐν ἡδονῇ κακῇ τὸ ἀποθανεῖν.