Plato, Laws 869c

τῶν γονέων τελευτήσεσθαι, παρέξει νόμος οὐδεὶς κτεῖναι τὸν πατέρα ἢ μητέρα, τοὺς εἰς φῶς τὴν ἐκείνου φύσιν ἀγαγόντας, ἀλλʼ ὑπομείναντα τὰ πάντα πάσχειν πρίν τι δρᾶν τοιοῦτον νομοθετήσει, πῶς τούτῳ δίκης γε ἄλλως προσῆκον τυγχάνειν ἂν γίγνοιτο ἐν νόμῳ; κείσθω δὴ τῷ πατέρα ἢ μητέρα ἀποκτείναντι θυμῷ θάνατος ἡ ζημία. ἀδελφὸς δὲ ἂν ἀδελφὸν κτείνῃ ἐν στάσεσι μάχης γενομένης ἤ τινι τρόπῳ τοιούτῳ,

father or mother, the very authors of his existence, even for the sake of saving his own life, and will ordain that he must suffer and endure everything rather than commit such an act,— in what other way than this can such a man be fittingly dealt with by law, and receive his due reward? Be it enacted, therefore, that for the man who in rage slays father or mother the penalty is death. If a brother kill a brother in fight during a civil war, or in any such way, acting in self-defence