Numbers 35:19-25

19The avenger of blood himself shall slay the murderer: when he meeteth him, he shall slay him. 20But if he shall thrust him of hatred, or hurl at him by laying in wait, that he die; 21Or in enmity shall smite him with his hand, that he die: he that smote him shall surely be put to death; for he is a murderer: the avenger of blood shall slay the murderer, when he meeteth him. 22But if he shall thrust him suddenly without enmity, or shall have cast upon him any thing without laying in wait, 23Or with any stone, by which a man may die, seeing him not, and shall cast it upon him, that he die, and was not his enemy, neither sought his harm: 24Then the congregation shall judge between the slayer and the avenger of blood according to these judgments: 25And the congregation shall deliver the slayer out of the hand of the avenger of blood, and the congregation shall restore him to the city of his refuge, where he had fled: and he shall abide in it to the death of the high priest, who was anointed with the holy oil.