The reason for grouping together these five laws, which are apparently so different from one another, as well as for attaching them to the previous regulations, is to be found in the desire to bring out distinctly the sacredness of life and of personal rights from every point of view, and impress it upon the covenant nation.
Expiation of a Murder Committed by an Unknown Hand. - Deu 21:1 and Deu 21:2. If any one was found lying in a field in the land of Israel (נֹפֵל fallen, then lying, Jdg 3:25; Jdg 4:22), having been put to death without its being known who had killed him (וגו נֹודַע לֹא, a circumstantial clause, attached without a copula, see Ewald, §341, b. 3), the elders and judges, sc., of the neighbouring towns, - the former as representatives of the communities, the latter as administrators of right, - were to go out and measure to the towns which lay round about the slain man, i.e., measure the distance of the body from the towns that were lying round about, to ascertain first of all which was the nearest town.
This nearest town was then required to expiate the blood-guiltiness, not only because the suspicion of the crime or of participation in the crime fell soonest upon it, but because the guilt connected with the shedding of innocent blood rested as a burden upon it before all others. To this end the elders were to take a heifer (young cow), with which no work had ever been done, and which had not yet drawn in the yoke, i.e., whose vital force had not been diminished by labour (see at Num 19:2), and bring it down into a brook-valley with water constantly flowing, and there break its neck. The expression, “it shall be that the city,” is more fully defined by “the elders of the city shall take.” The elders were to perform the act of expiation in the name of the city. As the murderer was not to be found, an animal was to be put to death in his stead, and suffer the punishment of the murderer. The slaying of the animal was not an expiatory sacrifice, and consequently there was no slaughtering and sprinkling of the blood; but, as the mode of death, viz., breaking the neck (vid., Exo 13:13), clearly shows, it was a symbolical infliction of the punishment that should have been borne by the murderer, upon the animal which was substituted for him. To be able to take the guilt upon itself and bear it, the animal was to be in the full and undiminished possession of its vital powers. The slaying was to take place in a אֵיתָן נַחַל, a valley with water constantly flowing through it, which was not worked (cultivated) and sown. This regulation as to the locality in which the act of expiation was to be performed was probably founded upon 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.
The priests were to come near during this transaction; i.e., some priests from the nearest Levitical town were to be present at it, not to conduct the affair, but as those whom Jehovah had chosen to serve Him and to bless in His name (cf. Deu 13:5), and according to whose mouth (words) every dispute and every stroke happened (cf. Deu 17:8), i.e., simply as those who were authorized by the Lord, and as the representatives of the divine right, to receive the explanation and petition of the elders, and acknowledge the legal validity of the act.
The elders of the town were to wash their hands over the slain heifer, i.e., to cleanse themselves by this symbolical act from the suspicion of any guilt on the part of the inhabitants of the town in the murder that had been committed (cf. Psa 26:6; Psa 73:13; Mat 27:24), and then answer (to the charge involved in what had taken place), and say, “Our hands have not shed this blood (on the singular שָׁפְכָה, see Ewald, §317, a.), and our eyes have not seen” (sc., the shedding of blood), i.e., we have neither any part in the crime nor any knowledge of it: “grant forgiveness (lit., 'cover up,' viz., the blood-guiltiness) to Thy people...and give not innocent blood in the midst of Thy people Israel,” i.e., lay not upon us the innocent blood that has been shed by imputation and punishment. “And the blood shall be forgiven them,” i.e., the bloodshed or murder shall not be imputed to them. On נִכַּפֵּר, a mixed form from the Niphal and Hithpael, see Ges. §55, and Ewald, §132, c.
In this way Israel was to wipe away the innocent blood (the bloodshed) from its midst (cf. Num 35:33). If the murderer were discovered afterwards, of course the punishment of death which had been inflicted vicariously upon the animal, simply because the criminal himself could not be found, would still fall upon him.