“If in the land that the LORD your God is giving you to possess someone is found slain, lying in the open country, and it is not known who killed him,
1. If one be found slain in the land. This Supplement: is of a mixed character, relating partly to the civil, and partly to the criminal law. We are informed by it how precious to God is the life of man; for, if a murder had been committed by some unknown person, He requires an expiation to be made, whereby the neighboring cities should purge...
Care had been taken by some preceding laws for the vigorous and effectual persecution of a wilful murderer (Deu 19:11 etc.), the putting of whom to death was the putting away of the guilt of blood from the land; but if this could not be done, the murderer not being discovered, they must not think that the land was in no danger of contracting any...
Commenting on Deuteronomy 21:1-9
If one be found slain,.... After public war with an enemy, Moses proceeds to speak of a private quarrel and fight of one man with another, in which one is slain, as Aben Ezra observes: in the land which the Lord thy God giveth thee to possess it; where murders might be committed more secretly, and remain undiscovered, when they came to live in separate...