So 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.
Numbers 35:33
Surrounding context
35:32 And 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.
35:33 So 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.
35:34 Therefore 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."'