Numbers 35:29-34

‘These things shall be for a statutory ordinance to you throughout your generations in all your dwellings. ‘If anyone kills a person, the murderer shall be put to death at the evidence of witnesses, but no person shall be put to death on the testimony of one witness. Moreover, you shall not take ransom for the life of a murderer who is guilty of death, but he shall surely be put to death. You shall not take ransom for him who has fled to his city of refuge, that he may return to live in the land before the death of the priest. So you shall not pollute the land in which you are; for blood pollutes the land and no expiation can be made for the land for the blood that is shed on it, except by the blood of him who shed it. You shall not defile the land in which you live, in the midst of which I dwell; for I the LORD am dwelling in the midst of the sons of Israel.’ ”