Numbers 35:29-32

29‘And these things shall be a statute of judgment to you throughout your generations in all your dwellings.

30Whoever kills a person, the murderer shall be put to death on the testimony of witnesses; but one witness is not sufficient testimony against a person for the death penalty.

31Moreover you shall take no ransom for the life of a murderer who is guilty of death, but he shall surely be put to death.

32And you shall take no ransom for him who has fled to his city of refuge, that he may return to dwell in the land before the death of the priest.