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.

Numbers 35:15

35:15 These six towns will be places of refuge for the Israelites, and for the foreigner, and for the settler among them, so that anyone who kills any person accidentally may flee there.

Numbers 35:22-23

35:22 “But if he strikes him suddenly, without enmity, or throws anything at him unintentionally, 35:23 or with any stone large enough that a man could die, without seeing him, and throws it at him, and he dies, even though he was not his enemy nor sought his harm,