Deuteronomy 21:4 - Joseph Benson’s Commentary on the Old and New Testaments

Unto a rough valley The Hebrew word נחל, nachal, here used, signifies either a valley or a torrent; and most probably is here meant of a valley with a brook running through it. For (Deu 21:6) the elders are required to wash their hands over the heifer, which seems to intimate that there was running water in the place. Which is neither eared nor sown Rough, uncultivated ground, fitly representing the horribleness of the murder. The Jews say, that unless, after this, the murderer was found, this valley was never to be tilled nor sown, which made the owners of the ground employ their utmost diligence to find out the murderer, that their land might not be waste for ever. But it is more natural to suppose, that such a rough and waste place was chosen partly that the horridness of it might beget a horror of the murder, and of the murderer, and partly because the blood of the victim would have polluted cultivated ground. For, though not slain at the altar, this was a kind of expiatory sacrifice, whereby the land was to be purged from the legal pollution contracted by the murder; and such sacrifices rendered every person or thing unclean that touched them. Shall strike off the heifer's neck To show what they should and would have done to the murderer, if they had found him.