Numbers 35:30–33

30 “If anyone kills a person, the murderer shall be put to death on the levidence of witnesses. But no person shall be put to death on the testimony of one witness. 31 Moreover, you shall accept no ransom for the life of a murderer, who is guilty of death, but he shall be put to death. 32 And you shall accept 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 high priest. 33 You shall not mpollute the land in which you live, for blood mpollutes the land, and no atonement can be made for the land for the blood that is shed in it, except nby the blood of the one who shed it.