A rough valley; literally, a stream of perpetuity, a perennial stream (cf. Psalms 74:15, Authorized Version, "mighty rivers;" Amos 5:24); but here rather the valley or wady through which a stream flowed, as is evident from its being described as neither eared—that is, ploughed (literally, wrought, tilled)—nor sown; a place which had not been profaned by the hand of man, but was in a state of nature.
"This regulation as to the locality in which the act of expiation was to be performed was probably founded on the idea that the water of the brook-valley would suck in the blood and clean it away, and that the blood sucked in by the earth would not be brought to light again by the ploughing and working of the soil" (Keil).
Strike off the heifer's neck there in the valley; rather, break the heifer's neck. As this was not an act of sacrifice, for which the shedding of blood would have been required, but simply a symbolical representation of the infliction of death on the undiscovered murderer, the animal was to be killed by breaking its neck (cf.