Numbers 35:29-31

29“ ‘This is to have the force of law for you throughout the generations to come, wherever you live.

30“ ‘Anyone who kills a person is to be put to death as a murderer only on the testimony of witnesses. But no one is to be put to death on the testimony of only one witness.

31“ ‘Do not accept a ransom for the life of a murderer, who deserves to die. They are to be put to death.