Numbers 35:30-34

Cities for the Levites

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. ³³So you shall not pollute the land where you are; for blood defiles the land, and no atonement can be made for the land, for the blood that is shed on it, except by the blood of him who shed it. ³⁴Therefore do not defile the land which you inhabit, in the midst of which I dwell; for I the Lord dwell among the children of Israel.’ ”