Numbers 35:6

35:6 Now from these towns that you will give to the Levites you must select six towns of refuge to which a person who has killed someone may flee. And you must give them forty-two other towns.

Numbers 35:12

35:12 And they must stand as your towns of refuge from the avenger in order that the killer may not die until he has stood trial before the community.

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,