Deuteronomy 19:13

9and if you keep all this commandment to do it, which I command you today, to love the LORD your God, and to walk ever in his ways, then you shall add three cities more for yourselves, in addition to these three.

10This is so that innocent blood will not be shed in the middle of your land which the LORD your God gives you for an inheritance, leaving blood guilt on you.

11But if any man hates his neighbor, lies in wait for him, rises up against him, strikes him mortally so that he dies, and he flees into one of these cities;

12then the elders of his city shall send and bring him there, and deliver him into the hand of the avenger of blood, that he may die.

13Your eye shall not pity him, but you shall purge the innocent blood from Israel that it may go well with you.

14You shall not remove your neighbor’s landmark, which they of old time have set, in your inheritance which you shall inherit, in the land that the LORD your God gives you to possess.

15One witness shall not rise up against a man for any iniquity, or for any sin that he sins. At the mouth of two witnesses, or at the mouth of three witnesses, shall a matter be established.

16If an unrighteous witness rises up against any man to testify against him of wrongdoing,

17then both the men, between whom the controversy is, shall stand before the LORD, before the priests and the judges who shall be in those days;