Numbers 35:30-33

MKJV(i) 30 Whoever kills any person, the murderer shall be put to death by the mouth of witnesses. But one witness shall not testify against any person to cause him to die. 31 And you shall take no ransom for the life of a murderer who is guilty of death. But he shall surely be put to death. 32 And you shall take no ransom for him who has fled to the city of his refuge, to return to live in the land until the death of the high priest. 33 So you shall not defile the land in which you are. For blood defiles the land. And the land cannot be cleansed of the blood that is shed in it, except by the blood of him that shed it.