Jamieson, Fausset and Brown on Numbers 35:29-34

29-34. these things shall be for a statute of judgment unto you throughout your generations--The law of the blood-avenger, as thus established by divine authority, was a vast improvement on the ancient practice of Goelism. By the appointment of cities of refuge, the manslayer was saved, in the meantime, from the blind and impetuous fury of vindictive relatives; but he might be tried by the local court, and, if proved guilty on sufficient evidence, condemned and punished as a murderer, without the possibility of deliverance by any pecuniary satisfaction. The enactment of Moses, which was an adaptation to the character and usages of the Hebrew people, secured the double advantage of promoting the ends both of humanity and of justice.