Plato, Laws 758a

μὲν τοῖν ἰσοτήτοιν ἀμφοῖν, ὡς δʼ ὅτι μάλιστα ἐπʼ ὀλιγίστοις τῇ ἑτέρᾳ, τῇ τῆς τύχης δεομένῃ.ταῦτα οὕτως διὰ ταῦτα, ὦ φίλοι, ἀναγκαῖον τὴν μέλλουσαν σῴζεσθαι δρᾶν πόλιν· ἐπειδὴ δὲ ναῦς τε ἐν θαλάττῃ πλέουσα φυλακῆς ἡμέρας δεῖται καὶ νυκτὸς ἀεί, πόλις τε ὡσαύτως ἐν κλύδωνι τῶν ἄλλων πόλεων διαγομένη καὶ παντοδαπαῖσιν ἐπιβουλαῖς οἰκεῖ κινδυνεύουσα ἁλίσκεσθαι, δεῖ δὴ διʼ ἡμέρας τε εἰς νύκτα καὶ ἐκ νυκτὸς συνάπτειν πρὸς

but that form, which needs good luck, we should employ as seldom as possible. The State which means to survive must necessarily act thus, my friends, for the reasons we have stated. For just as a ship when sailing on the sea requires continual watchfulness both by night and day, so likewise a State, when it lives amidst the surge of surrounding States and is in danger of being entrapped by all sorts of plots, requires to have officers linked up with officers from day to night and from night to day,