Joshua 20:9

These were the cities designated for all the people of Israel and for the stranger sojourning among them, that anyone who killed a person without intent could flee there, so that he might not die by the hand of the avenger of blood , till he stood before the congregation .

Any of the Israelites or any foreigner residing among them who killed someone accidentally could flee to these designated cities and not be killed by the avenger of blood prior to standing trial before the assembly.

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. Joshua 19 Books Joshua 21