Plato, Laws 730d

καὶ μὴ ἑταίρων καὶ παίδων σχεδὸν ὁμοίως ὀρφανὸν αὐτῷ γενέσθαι τὸν βίον. τίμιος μὲν δὴ καὶ ὁ μηδὲν ἀδικῶν, ὁ δὲ μηδʼ ἐπιτρέπων τοῖς ἀδικοῦσιν ἀδικεῖν πλέον ἢ διπλασίας τιμῆς ἄξιος ἐκείνου· ὁ μὲν γὰρ ἑνός, ὁ δὲ πολλῶν ἀντάξιος ἑτέρων, μηνύων τὴν τῶν ἄλλων τοῖς ἄρχουσιν ἀδικίαν. ὁ δὲ καὶ συγκολάζων εἰς δύναμιν τοῖς ἄρχουσιν, ὁ μέγας ἀνὴρ ἐν πόλει καὶ τέλειος, οὗτος ἀναγορευέσθω νικηφόρος ἀρετῇ.

a complete solitude, wherein his life becomes almost equally desolate whether his companions and children are living or dead. He that does no wrong is indeed a man worthy of honor; but worthy of twice as much honor as he, and more, is the man who, in addition, consents not to wrongdoers when they do wrong; for while the former counts as one man, the latter counts as many, in that he informs the magistrates of the wrongdoing of the rest. And he that assists the magistrates in punishing, to the best of his power, let him be publicly proclaimed to be the Great Man of the State and perfect, the winner of the prize for excellence.