Numbers 35:25-29

And 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.

But if at any time he goes beyond the border of his city of refuge to which he flees,

and the blood avenger finds him outside the border of his city of refuge, and the blood avenger kills him, he will not be guilty of bloodshed,

because 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.

‘These things shall be a statutory ordinance for you throughout your generations in all your dwelling places.