Numbers 35:11

35:11 you must then designate some towns as towns of refuge for you, to which a person who has killed someone unintentionally may flee.

Exodus 21:13

21:13 But if he does not do it with premeditation, but it happens by accident, then I will appoint for you a place where he may flee.

Deuteronomy 19:5

19:5 Suppose he goes with someone else to the forest to cut wood and when he raises the ax to cut the tree, the ax head flies loose from the handle and strikes his fellow worker so hard that he dies. The person responsible may then flee to one of these cities to save himself.

Joshua 20:3

20:3 Anyone who accidentally kills someone can escape there; these cities will be a place of asylum from the avenger of blood.

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.