Plato, Republic, book 1 140:

φήσεισ δὲ καὶ ἀσπίδα καὶ λύραν ὅταν δέῃ φυλάττειν καὶ μηδὲν χρῆσθαι, χρήσιμον εἶναι τὴν δικαιοσύνην, ὅταν δὲ χρῆσθαι, τὴν ὁπλιτικὴν καὶ τὴν μουσικήν;