Ancient character of this custom. The shedding of blood during a raid starts a blood feud which may continue for many years. The basis for this feud is a custom or law that is common among many Semitic people. The unit of society among these peoples is the tribe or clan. The members of any one tribe have a responsibility to punish anybody who wrongs a member of their clan.
The blood of a murdered member of the tribe "crieth . . . from the ground" (Genesis 4:10), and the nearest male relative is especially duty bound to avenge the murder.
In olden times, instead of the state executing a murderer, it became the duty of the kinsman to avenge the death of the relative. The law of Moses recognized this right of the kinsman, but it did protect one who killed by accident and not by purpose, and so provided the cities of refuge, where such a man might flee and receive justice. "These six cities shall be a refuge, both for the children of Israel, and for the stranger, and for the sojourner among them: that every one that killeth any person unawares may flee thither" (Numbers 35:15). But these cities of refuge were no protection for a real murderer. He was turned over to the kinsman for vengeance.
"The revenger of blood [i.e., the kinsman] himself shall slay the murderer: when he meeteth him, he shall slay him" (Numbers 35:19).
[Manners And Customs of Bible Lands]
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