Ignatius of Antioch, Epistle to the Magnesians 10
So let us not be numb to his kindness. If he were to imitate the way we behave, we would cease to exist. Since we have become his disciples, then, let us learn to live by Christianity. Whoever goes by any other name than this does not belong to God.
Get rid of the bad leaven, gone stale and sour, and be changed into the new leaven, which is Jesus Christ (1 Corinthians 5:7–8). Be salted in him, so that none of you rots, for by your smell you will be found out.
It is absurd to talk of Jesus Christ and practice Judaism. Christianity did not put its faith in Judaism; Judaism put its faith in Christianity, where every tongue that believes in God has been gathered.
Greek
Μὴ οὖν ἀναισθητῶμεν τῆς χρηστότητος αὐτοῦ. ἐὰν γὰρ ἡμᾶς μιμήσηται καθὰ πράσσομεν, οὐκέτι ἐσμέν. διὰ τοῦτο, μαθηταὶ αὐτοῦ γενόμενοι, μάθωμεν κατὰ Χριστιανισμὸν ζῆν. ὃς γὰρ ἄλλῳ ὀνόματι καλεῖται πλέον τούτου, οὐκ ἔστιν τοῦ θεοῦ.
ὑπέρθεσθε οὖν τὴν κακὴν ζύμην, τὴν παλαιωθεῖσαν καὶ ἐνοξίσασαν, καὶ μεταβάλεσθε εἰς νέαν ζύμην, ὅ ἐστιν Ἰησοῦς Χριστός. ἁλίσθητε ἐν αὐτῷ, ἵνα μὴ διαφθαρῇ τις ἐν ὑμῖν, ἐπεὶ ἀπὸ τῆς ὀσμῆς ἐλεγχθήσεσθε.
ἄτοπόν ἐστιν, Ἰησοῦν Χριστὸν λαλεῖν καὶ ἰουδαΐζειν. ὁ γὰρ Χριστιανισμὸς οὐκ εἰς Ἰουδαῖσμὸν ἐπίστευσεν, ἀλλ’ Ἰουδαϊσμὸς εἰς Χριστιανισμόν, ᾧ πᾶσα γλῶσσα πιστεύσασα εἰς θεὸν συνήχθη.