Plato, Letters 334b

καὶ εἰς τὸν ἔπειτα μελήσει χρόνον—τὸ δὲ Ἀθηναίων πέρι λεγόμενον, ὡς αἰσχύνην οὗτοι περιῆψαν τῇ πόλει, ἐξαιροῦμαι· φημὶ γὰρ κἀκεῖνον Ἀθηναῖον εἶναι ὃς οὐ προύδωκεν τὸν αὐτὸν τοῦτον, ἐξὸν χρήματα καὶ ἄλλας τιμὰς πολλὰς λαμβάνειν. οὐ γὰρ διὰ βαναύσου φιλότητος ἐγεγόνει φίλος, διὰ δὲ ἐλευθέρας παιδείας κοινωνίαν, ᾗ μόνῃ χρὴ πιστεύειν τὸν νοῦν κεκτημένον μᾶλλον ἢ συγγενείᾳ ψυχῶν καὶ σωμάτων· ὥστε οὐκ ἀξίω

But I do take exception to what is said about the Athenians, that these men covered their city with shame; for I asselt that it was also an Athenian who refused to betray the very same man when, by doing so, he might have gained wealth and many other honors. For he had become his friend not in the bonds of a venal friendship but owing to association in liberal education; since it is in this alone that the judicious man should put his trust, rather than in kinship of soul or of body. Consequently, the two murderers