Matthew Poole and continuators on Joshua 20:9

9 These were the cities appointed for all the children of Israel, and for the stranger that sojourneth among them, that whosoever killeth any person at unawares, might flee thither, and not die by the hand of the avenger of blood, until he stood before the congregation.

Not onely Proselites, but others also; because this was a matter of common right, that a distinction might be made between casual Man-slayers, and wilful Murderers.