Plato, Laws 944d

ἔστω δίκη ῥιφθέντων, τῆς δὲ εἰρημένης ἔμπροσθεν ὁ δικάζων μὴ ἀμελείτω σκοπεῖν. τὸν γὰρ κακὸν ἀεὶ δεῖ κολάζειν, ἵνʼ ἀμείνων ᾖ, οὐ τὸν δυστυχῆ· οὐδὲν γὰρ πλέον. ζημία δὴ τῷ τὴν τοιαύτην ἀμυντηρίων ὅπλων εἰς τοὐναντίον ἀφέντι δύναμιν τίς ἄρα γίγνοιτʼ ἂν πρόσφορος; οὐ γὰρ δυνατὸν ἀνθρώπῳ δρᾶν τοὐναντίον ὥς ποτε θεόν φασι δρᾶσαι, Καινέα τὸν Θετταλὸν ἐκ γυναικὸς μεταβαλόντα εἰς ἀνδρὸς φύσιν· ἦν γὰρ ἀνδρὶ ῥιψάσπιδι τρόπον τινὰ πρέπουσα πασῶν

For the bad man one must always punish, in order to better him, but not the luckless man; for that profits not. What, then, would be a proper penalty for the man who has thrown away for naught such powerful weapons of defence? A god, it is said, once changed Kaineus the Thessalian from woman’s shape to man’s; but it is beyond human power to do the opposite of this; otherwise,