Numbers 35:25-28

25And the congregation shall rescue the manslayer from the hand of the avenger of blood, and the congregation shall restore him to his city of refuge to which he had fled, and he shall live in it until the death of the high priest who was anointed with the holy oil.

26But if the manslayer shall at any time go beyond the boundaries of his city of refuge to which he fled,

27and the avenger of blood finds him outside the boundaries of his city of refuge, and the avenger of blood kills the manslayer, he shall not be guilty of blood.

28For he must remain in his city of refuge until the death of the high priest, but after the death of the high priest the manslayer may return to the land of his possession.