Numbers 35:30-33

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.

32“ ‘Do not accept a ransom for anyone who has fled to a city of refuge and so allow them to go back and live on their own land before the death of the high priest.

33“ ‘Do not pollute the land where you are. Bloodshed pollutes the land, and atonement cannot be made for the land on which blood has been shed, except by the blood of the one who shed it.