For blood it defileth the land - The very land was considered as guilty till the blood of the murderer was shed in it. No wonder God is so particularly strict in his laws against murderers,
1. Because he is the author of life, and none have any right to dispose of it but himself.
2. Because life is the time to prepare for the eternal world, and on it the salvation of the soul accordingly depends; therefore it is of infinite consequence to the man that his life be lengthened out to the utmost limits assigned by Divine Providence. As he who takes a man's life away before his time may be the murderer of his soul as well as of his body, the severest laws should be enacted against this, both to punish and prevent the crime.
The Mosaic cities of refuge have in general been considered, not merely as civil institutions, but as types or representations of infinitely better things; and in this light St. Paul seems to have considered them and the altar of God, which was a place of general refuge, as it is pretty evident that he had them in view when writing the following words: "God, willing more abundantly to show unto the heirs of promise the immutability of his counsel, confirmed it by an oath; that by two immutable things, (his oath and promise), in which it was impossible for God to lie, we might have a strong consolation who have Fled for Refuge to lay Hold upon the Hope set before us," Heb 6:17, Heb 6:18. Independently of this, it was a very wise political institute; and while the patriarchal law on this point continued in force, this law had a direct tendency to cool and moderate the spirit of revenge, to secure the proper accomplishment of the ends of justice, and to make way for every claim of mercy and equity. But this is not peculiar to the ordinance of the cities of refuge; every institution of God is distinguished in the same way, having his own glory, in the present and eternal welfare of man, immediately in view.

So ye shall not pollute the land wherein ye are,.... The land of Canaan, as it had been by the old inhabitants of it, by idolatry, adultery, and murder:

for blood it defileth the land: the shedding of innocent blood defiles a nation, and the inhabitants of it, brings guilt thereon, and subjects to punishment:

and the land cannot be cleansed of the blood that is shed therein, but by the blood of him that shed it; or "there can be no expiation" (b), or "atonement made" for it in any other way; the blood of the murderer is required at his hands, and nothing short of it will satisfy law and justice, see Gen 9:6.

(b) "non posset expiatio", Junius & Tremellius, Piscator; to the same sense Pagninus, Montanus, Tigurine version.

these things shall be for a statute of judgment unto you throughout your generations--The law of the blood-avenger, as thus established by divine authority, was a vast improvement on the ancient practice of Goelism. By the appointment of cities of refuge, the manslayer was saved, in the meantime, from the blind and impetuous fury of vindictive relatives; but he might be tried by the local court, and, if proved guilty on sufficient evidence, condemned and punished as a murderer, without the possibility of deliverance by any pecuniary satisfaction. The enactment of Moses, which was an adaptation to the character and usages of the Hebrew people, secured the double advantage of promoting the ends both of humanity and of justice.

Next: Numbers Chapter 36