Numbers 35:25-28

25And the congregation shall save the one who committed manslaughter from the hand of the blood avenger, and the congregation shall return him to his city of refuge to which he fled; and he shall live in it until the death of the high priest who was anointed with the holy oil. 26But if at any time 1he goes beyond the border of his city of refuge to which he flees, 27and the blood avenger finds him outside the border of his city of refuge, and the blood avenger kills 2him, he 3will not be guilty of bloodshed, 28because he should have remained in his city of refuge until the death of the high priest. But after the death of the high priest the one who committed manslaughter may return to the land of his property.