Plato, Laws 645a

δʼ εἶναι τὴν τοῦ λογισμοῦ ἀγωγὴν χρυσῆν καὶ ἱεράν, τῆς πόλεως κοινὸν νόμον ἐπικαλουμένην, ἄλλας δὲ σκληρὰς καὶ σιδηρᾶς, τὴν δὲ μαλακὴν ἅτε χρυσῆν οὖσαν, τὰς δὲ ἄλλας παντοδαποῖς εἴδεσιν ὁμοίας. δεῖν δὴ τῇ καλλίστῃ ἀγωγῇ τῇ τοῦ νόμου ἀεὶ συλλαμβάνειν· ἅτε γὰρ τοῦ λογισμοῦ καλοῦ μὲν ὄντος, πρᾴου δὲ καὶ οὐ βιαίου, δεῖσθαι ὑπηρετῶν αὐτοῦ τὴν ἀγωγήν, ὅπως ἂν ἐν ἡμῖν τὸ χρυσοῦν γένος νικᾷ τὰ ἄλλα

it is the leading-string, golden and holy, of calculation, entitled the public law of the State; and whereas the other cords are hard and steely and of every possible shape and semblance, this one is flexible and uniform, since it is of gold. With that most excellent leading-string of the law we must needs co-operate always; for since calculation is excellent, but gentle rather than forceful, its leading-string needs helpers to ensure that the golden kind within us may vanquish the other kinds.