Deuteronomy 21:4

Ver. 4. Unto a rough valley, &c.— Unto a watered valley. Schult, p. 248. The heifer was to be brought into an uncultivated ground, (probably with a brook running through it, as the elders are required to wash their hands over the heifer, ver. 6.) as some say, to represent the horridness of the murder. We are told, that the place might never be plowed or sown thereafter; which made the owners of the ground employ their utmost diligence to find out the murderer, that their land might not lie waste for ever. But a more just explication is, that some desolate piece of ground was to be chosen, because the blood of the victim would have polluted cultivated ground: for this was a kind of expiatory sacrifice, whereby the land was cleansed from the legal pollution of murder; and such sacrifices rendered every person or thing unclean which touched them. See Leviticus 16:26. In this valley they were to strike off the neck of the heifer, as an emblem of the punishment which the assassin deserved, and as a representation of his crime.