Numbers 35:26-28

MKJV(i) 26 But if the one who killed shall at any time come outside the border of the city of his refuge to which he had fled, 27 and if the avenger of blood finds him outside the borders of the city of his refuge, and if the avenger of blood kills the slayer, he shall not be guilty of blood, 28 because he should have remained in the city of his refuge until the death of the high priest. But after the death of the high priest the one who killed shall return to the land of his possession.