Numbers 35:26-28

But if the killer ever goes beyond the limits of the city of refuge he fled to,

and the next-of-kin avenger finds him outside the limits of his city of refuge, and the avenger kills the killer, he will not be guilty of the man's blood;

because he must stay in his city of refuge until the death of the cohen hagadol. But after the death of the cohen hagadol the killer may return to the land he owns.