Numbers 35:22-28

22But if he have thrust at him suddenly without enmity, or have cast upon him anything unintentionally,

23or [have smitten him] with any stone wherewith one may die, without seeing him, and have cast it upon him so that he die, and he was not his enemy, neither sought his harm:

24then the assembly shall judge between the smiter and the avenger of blood according to these judgments;

25and the assembly shall rescue the manslayer out of the hand of the avenger of blood, and the assembly shall restore him to the city of his refuge, whither he had fled; and he shall abide in it until the death of the high-priest, who was anointed with the holy oil.

26But if the manslayer shall in any way come outside the limits of the city of his refuge whither he hath fled,

27and the avenger of blood find him outside the limits of his city of refuge, and the avenger of blood kill the manslayer, there shall be no blood-guiltiness upon him;

28for the manslayer should have remained in the city of his refuge until the death of the high-priest; but after the death of the high-priest he may return into the land of his possession.