Plato, Laws 868c

ἐθέλωσι, πλὴν μηδαμῇ μηδαμῶς ζωγροῦντας, καθαροὺς εἶναι· ἐὰν δὲ ἄλλος τις δοῦλος ἐλεύθερον ἀποκτείνῃ θυμῷ, παραδιδόντων οἱ δεσπόται τὸν δοῦλον τοῖς προσήκουσι τοῦ τελευτήσαντος, οἱ δὲ ἐξ ἀνάγκης μὲν θανατωσάντων τὸν δράσαντα, τρόπῳ δὲ ᾧ ἂν ἐθέλωσιν. ἂν δʼ, ὃ γίγνεται μέν, ὀλιγάκις δέ, διὰ θυμὸν πατὴρ ἢ μήτηρ ὑὸν ἢ θυγατέρα πληγαῖς ἤ τινι τρόπῳ βιαίῳ κτείνῃ, καθάρσεις μὲν τὰς αὐτὰς τοῖς ἄλλοις καθαιρέσθω καὶ ἐνιαυτοὺς τρεῖς ἀπενιαυτεῖν,

in any wise let him live,—and shall be held guiltless. And if a slave kill a free man (other than his master) in rage, his masters shall hand over the slave to the kindred of the dead man, and they shall be compelled to put the criminal to death, doing so in whatever manner they choose. If in a fit of rage a father or mother slays a son or daughter by means of blows or some kind of violence,—an occurrence which, though rare, does sometimes happen,—the slayer must make the same purifications as the other slayers, and be exiled for three years;