Joshua 20:5

20:5 When the avenger of blood comes after him, they must not hand over to him the one who committed manslaughter, for he accidentally killed his fellow man without premeditation.

Joshua 20:9

20:9 These were the cities of refuge appointed for all the Israelites and for resident foreigners living among them. Anyone who accidentally killed someone could escape there and not be executed by the avenger of blood, at least until his case was reviewed by the assembly.