In ancient Israel, as in tribal societies in general, the members of the clan were responsible for avenging the death of innocent victims. Unavenged blood cries out to the Lord (Gen. 4.10). Innocent blood defiles the land and must be expiated (Num. 35.31–34), and this is the duty of the avenger.
As government became more centralized, the prerogative of blood revenge was slowly taken out of the hands of the clan. Under the monarchy it appears that the king had the power to intervene and even to grant immunity from the avenger (2 Sam. 14.8–11), but the right of “blood redemption” remained a sacred duty. In Roman times the Jews were no longer permitted to carry out blood revenge (John 18.31). According to Paul, it is not the duty of the individual but that of the state to avenge evil on behalf of God (Rom. 13.4; cf. Ps. 9.12; 2 Kings 9.7; Rev. 19.2).
The execution of a criminal by the authorized authorities did not of course call for blood revenge, nor did the killing of a person in self‐defense. Only murder and involuntary homicide demanded it. Even a homicidal beast was considered bloodguilty and had to be stoned (Exod. 21.28–32). The next of kin, usually the nearest male relative, who put a person who committed homicide to death, was called “the redeemer of blood” (Num. 35.19: Hebr. gōʾēl haddām; cf. the use of gōʾel in Ruth 3.9–4.8; See Redeem).
For those who accidentally killed an innocent person there were provisions of asylum. The altar of Yahweh was such a refuge (Exod. 21.12–14; 1 Kings 1.50–53; 2.28–34). More important were the Levitical cities of refuge, three on either side of Jordan, to which the person who killed someone accidentally could flee (Num. 35.6–15). Those guilty of murder had no refuge but were to be executed after a judicial inquiry (Deut. 19.11–13). Since life was viewed as sacred (Gen. 9.6), no amount of money could be given as recompense for the loss of the life of an innocent person; it had to be “life for life” (Exod. 21.23; Deut. 19.21). By observing this law of retribution Israel was spared violence and endless blood feuds.