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 35:16

35:16 “But if he hits someone with an iron tool so that he dies, he is a murderer. The murderer must surely be put to death.

Numbers 35:19

35:19 The avenger of blood himself must kill the murderer; when he meets him, he must kill him.