The Law Concerning Unsolved Murder (Deuteronomy 21)

in  he land your God is giving you to possess, and it is not known who killed him, and then the elders and your judges shall go out, and they shall measure the distance from the slain man to the surrounding cities.  And it shall be that the elders of the city nearest to the slain man will take a heifer which has not been worked and which has not pulled with a yoke; and the elders of that city shall bring the heifer down to valley with flowing water, which is neither plowed nor sown,...........................................