Numbers 35:22-27

“But if he pushed him suddenly without enmity, or hurled anything on him without lying in wait or used a stone that could cause death, and without seeing him dropped it on him, so that he died, though he was not his enemy and did not seek his harm, then the congregation shall judge between the manslayer and the avenger of blood, in accordance with these rules. And the congregation shall rescue the manslayer from the hand of the avenger of blood, and the congregation shall restore him to his city of refuge to which he had fled, and he shall live in it until the death of the high priest who was anointed with the holy oil. But if the manslayer shall at any time go beyond the boundaries of his city of refuge to which he fled, and the avenger of blood finds him outside the boundaries of his city of refuge, and the avenger of blood kills the manslayer, he shall not be guilty of blood.