Plato, Laws 647b

καὶ μέγιστον κακὸν ἰδίᾳ τε καὶ δημοσίᾳ πᾶσι νενόμικεν; ὀρθῶς λέγεις. οὐκοῦν τά τʼ ἄλλα πολλὰ καὶ μεγάλα ὁ φόβος ἡμᾶς οὗτος σῴζει, καὶ τὴν ἐν τῷ πολέμῳ νίκην καὶ σωτηρίαν ἓν πρὸς ἓν οὐδὲν οὕτως σφόδρα ἡμῖν ἀπεργάζεται; δύο γὰρ οὖν ἐστὸν τὰ τὴν νίκην ἀπεργαζόμενα, θάρρος μὲν πολεμίων, φίλων δὲ φόβος αἰσχύνης πέρι κακῆς. ἔστι ταῦτα. ἄφοβον ἡμῶν ἄρα δεῖ γίγνεσθαι καὶ φοβερὸν

both publicly and privately, a very great evil? Quite right. And does not this fear, besides saving us in many other important respects, prove more effective than anything else in ensuring for us victory in war and security? For victory is, in fact, ensured by two things, of which the one is confidence towards enemies, the other, fear of the shame of cowardice in the eyes of friends. That is so. Thus each one of us ought to become both fearless and fearful;