Numbers 35:26-28

MSB(i) 26 But if the manslayer ever goes outside the limits of the city of refuge to which he fled 27 and the avenger of blood finds him outside of his city of refuge and kills him, then the avenger will not be guilty of bloodshed 28 because the manslayer must remain in his city of refuge until the death of the high priest. Only after the death of the high priest may he return to the land he owns.