Numbers 35:16-24, 30-31

And if he smite him with an instrument of iron, so that he die, he is a murderer: the murderer shall surely be put to death. And if he smite him with throwing a stone, wherewith he may die, and he die, he is a murderer: the murderer shall surely be put to death. Or if he smite him with an hand weapon of wood, wherewith he may die, and he die, he is a murderer: the murderer shall surely be put to death. The revenger of blood himself shall slay the murderer: when he meeteth him, he shall slay him. But if he thrust him of hatred, or hurl at him by laying of wait, that he die; or in enmity smite him with his hand, that he die: he that smote him shall surely be put to death; for he is a murderer: the revenger of blood shall slay the murderer, when he meeteth him. But if he thrust him suddenly without enmity, or have cast upon him any thing without laying of wait, or with any stone, wherewith a man may die, seeing him not, and cast it upon him, that he die, and was not his enemy, neither sought his harm: then the congregation shall judge between the slayer and the revenger of blood according to these judgments

Whoso killeth any person, the murderer shall be put to death by the mouth of witnesses: but one witness shall not testify against any person to cause him to die. Moreover ye shall take no satisfaction for the life of a murderer, which is guilty of death: but he shall be surely put to death.