Numbers 35:33
So ye shall not pollute the land wherein ye are: for blood it defileth the land: and the land cannot be cleansed of the blood that is shed therein, but by the blood of him that shed it. So ye shall not pollute the land wherein ye are: for blood it defileth the land: and the land cannot be cleansed of the blood that is shed therein, but by the blood of him that shed it.
When intentional killing is proved, the guilty murderer must surely be put to death. No atonement can rescue him, no satisfaction can be accepted for him, and no ransom can deliver him from the sentence. Even if he flees for refuge to the altar, he must be taken from there to die.
Blood that is shed defiles the land wherein the people live. That land cannot be cleansed of the blood shed in it except by the blood of the one who shed it. This severe punishment is demanded by the safety of the nation and by its purity. Human life is given by God alone, and therefore it must be sacredly guarded.