Numbers 35:31-34

35:31 Moreover, you must not accept a ransom for the life of a murderer who is guilty of death; he must surely be put to death. 35:32 And you must not accept a ransom for anyone who has fled to a town of refuge, to allow him to return home and live on his own land before the death of the high priest.

35:33 “You must not pollute the land where you live, for blood defiles the land, and the land cannot be cleansed of the blood that is shed there, except by the blood of the person who shed it. 35:34 Therefore do not defile the land that you will inhabit, in which I live, for I the Lord live among the Israelites.”