Numbers 35:29-32

29These are legal requirements for you to observe from generation to generation, wherever you may live.

30“All murderers must be put to death, but only if evidence is presented by more than one witness. No one may be put to death on the testimony of only one witness.

31Also, you must never accept a ransom payment for the life of someone judged guilty of murder and subject to execution; murderers must always be put to death.

32And never accept a ransom payment from someone who has fled to a city of refuge, allowing a slayer to return to his property before the death of the high priest.