Plato
Laws (Book 9, p. 865)
[865a] (...) 'We need not hesitate to enact laws about every class of murder on similar lines, now that we have made a beginning. First we shall deal with the cases that are violent and involuntary. If a man has killed a friend in a contest or in public games—whether his death has been immediate or as the after-effect of wounds,—or similarly if he has killed him in war or in some action of training for war, either when practicing [865b] javelin-work without armor or when engaged in some warlike maneuver in heavy armor,—then, when he has been purified as the Delphic rule on this matter directs, he shall be accounted pure. So too with respect to all doctors, if the patient dies against the will of his doctor, the doctor shall be accounted legally pure. And if one man kills another of his own act, but involuntarily,—whether it be with his own unarmed body, or by a tool or a weapon, or by a dose of drink or of solid food, or by application of fire or of cold, or by deprivation of air, and whether he does it himself with his own body or by means of other bodies,— [865c] in all cases it shall be accounted to be his own personal act, and he shall pay the following penalties. If he kill a slave, he shall secure the master against damage and loss, reckoning as if it were a slave of his own that had been destroyed, or else he shall be liable to a penalty of double the value of the dead man,—and the judges shall make an assessment of his value,—and he must also employ means of purification greater and more numerous than those employed by persons [865d] who kill a man at games, and those interpreters1 whom the oracle names shall be in charge of these rites; but if it be a slave of his own that he has killed, he shall be set free after the legal purification. And if anyone kill a free man involuntarily, he shall undergo the same purifications as the man that has killed a slave; and there is an ancient tale, told of old, to which he must not fail to pay regard. The tale is this,—that the man slain by violence, who has lived in a free and proud spirit, is wroth with his slayer when newly slain, [865e] and being filled also with dread and horror on account of his own violent end, when he sees his murderer going about in the very haunts which he himself had frequented, he is horror-stricken; and being disquieted himself, he takes conscience as his ally, and with all his might disquiets his slayer—both the man himself and his doings. Wherefore it is right for the slayer to retire before his victim for a full year, in all its seasons, and to vacate all the spots he owned in all parts of his native land; and if the dead man be a Stranger, he shall be barred also from the Stranger's country.'