NOTES for Num 35:1-34
In establishing for His people the boundaries of the land He had defined for them, God especially points out the need to set apart special so-called cities of refuge on it. The matter concerns such places where a person who had committed an unintentional or simply accidental killing could avoid the vengeance of blood avengers. The fact is that, according to the norms of customary law rooted back in the common Semitic era, any blood that was shed demanded vengeance, regardless of whether the bloodshed was accidental, unintentional, or deliberate.
Here there was a clearly magical approach, connected with the idea that the shedding of blood defiles in itself, and that one must be cleansed from defilement. At the same time it was thought that the defilement affected all the relatives of the slain person if they did not avenge him on the killer: for refusal to take vengeance meant a kind of indirect complicity in the killing. A blood avenger who could take vengeance but did not use this opportunity became, as it were, an accomplice in the killing, even if not directly but indirectly. Therefore, if there was an opportunity to find the killer and kill him, every blood avenger (and in a patriarchal clan society every kinsman of the slain person was one) had to do it.
Meanwhile, in God's eyes, of course, there was a difference between intentional murder, when a person from the very beginning wanted to kill and did kill, and killing through negligence or simply without intent - for example, in the heat of the moment, or in a fight during which the person did not intend to kill anyone but, as sometimes happens, misjudged the force of the blow. It was for such involuntary killers, who according to the laws of the Torah did not deserve the death penalty, that the cities of refuge were created. Here it was important not only to save from blood vengeance those who were not intentional murderers, but also to show everyone that in relationships between people there should be no place for anything magical, even when the issue is the magic of shed blood - for this kind of magical thinking not only divides people from one another, but also separates them from God.