Numbers 35:22-27

‘However, if he pushes him suddenly without enmity, or throws anything at him without lying in wait, or uses a stone, by which a man could die, throwing it at him without seeing him, so that he dies, while he was not his enemy or seeking his harm, then the congregation shall judge between the manslayer and the avenger of blood according to these judgments. So the congregation shall deliver the manslayer from the hand of the avenger of blood, and the congregation shall return him to the city of refuge where he had fled, and he shall remain there until the death of the high priest who was anointed with the holy oil. But if the manslayer at any time goes outside the limits of the city of refuge where he fled, and the avenger of blood finds him outside the limits of his city of refuge, and the avenger of blood kills the manslayer, he shall not be guilty of blood