Deuteronomy 21:9

Ver. 9. So shalt thou put away the guilt of innocent blood— Till this was done, the guilt was to be looked upon as national; but upon this solemn performance the government was deemed to have discharged its duty, and the nation was cleared of all guilt in the matter. This law, we see, made provision to purify a neighbouring city, and in a solemn manner by their magistrates, from any knowledge of a murder in which they had no hand, and to which they were no way privy; to keep up an abhorrence of the crime, and a care to prevent or detest it: in which particular it is remarkable that no ancient lawgiver has been more exact than Moses. The Greeks had some good rules respecting this matter; and Plato, in particular, ordered, that, "upon the finding a murdered body, public declaration should be made, that the murderer (if he could not be discovered) should banish himself immediately from his country." De Leg. vol. 2: lib. 2.