Commentary on the Bible, by Adam Clarke, [1831], at sacred-texts.com
If a man be found slain in a field, and the cause of his death be unknown, the murder shall be expiated by the sacrifice of a heifer in an uncultivated valley, Deu 21:1-4. The rites to be used on the occasion, Deu 21:5-9. The ordinance concerning marriage with a captive, Deu 21:10-14. The law relative to the children of the hated and beloved wives: if the son of the hated wife should be the first-born he shall not be disinherited by the son of the beloved wife, but shall have a double portion of all his father's goods, Deu 21:15-18. The law concerning the stubborn and rebellious son, who, when convicted, is to be stoned to death, Deu 21:19-21. Of the person who is to be hanged, Deu 21:22. His body shall not be left on the tree all night; every one that is hanged on a tree is accursed of God, Deu 21:23.
Shall bring down the heifer unto a rough valley - נחל איתן nachal eythan might be translated a rapid stream, probably passing through a piece of uncultivated ground where the elders of the city were to strike off the head of the heifer, and to wash their hands over her in token of their innocence. The spot of ground on which this sacrifice was made must be uncultivated, because it was considered to be a sacrifice to make atonement for the murder, and consequently would pollute the land. This regulation was calculated to keep murder in abhorrence, and to make the magistrates alert in their office, that delinquents might be discovered and punished, and thus public expense saved.
Shall wash their hands over the heifer - Washing the hands, in reference to such a subject as this, was a rite anciently used to signify that the persons thus washing were innocent of the crime in question. It was probably from the Jews that Pilate learned this symbolical method of expressing his innocence.
And seest - a beautiful woman - No forcible possession was allowed even in this case, when the woman was taken in war, and was, by the general consent of ancient nations, adjudged as a part of the spoils. The person to whose lot or share such a woman as is here described fell, might, if he chose, have her for a wife on certain conditions; but he was not permitted to use her under any inferior character.
She shall shave her head - This was in token of her renouncing her religion, and becoming a proselyte to that of the Jews. This is still a custom in the East; when a Christian turns Mohammedan his head is shaven, and he is carried through the city crying, la alahila allah we Mohammed resooli Allah; "There is no God but God, and Mohammed is the prophet of God."
Pare her nails - ועשתה את צפרניה veasethah eth tsipporneyha, "she shall make her nails." Now whether this signifies paring or letting them grow, is greatly doubted among learned men. Possibly it means neither, but colouring the nails, staining them red with the hennah, which is much practiced in India to the present day, and which was undoubtedly practiced among the ancient Egyptians, as is evident from the nails of mummies which are found thus stained. The hennah, according to Hasselquist, grows in India, and in Upper and Lower Egypt; it flowers from May to August. The manner of using it is this: the leaves are powdered, and made into a paste with water: they bind this paste on the nails of their fingers and toes, and let it stand on all night; in the morning they are found to be of a beautiful reddish yellow, and this lasts three weeks or a month, after which they renew the application. They often stain the palms of their hands and the soles of their feet in the same way, as appears from many paintings of eastern ladies done in India and Persia, which now lie before me. This staining the soles of the feet with the hennah is probably meant in Sa2 19:24 : Mephibosheth had not dressed (literally made) his feet - they had not been thus coloured.
One beloved, and another hated - That is, one loved less than the other. This is the true notion of the word hate in Scripture. So Jacob Hated Leah, that is, he loved her less than he did Rachel; and Jacob have I loved, but Esau have I Hated, that is, I have shown a more particular affection to the posterity of Jacob than I have to the posterity of Esau. See the note on Gen 29:31. From this verse we see that polygamy did exist under the Mosaic laws, and that it was put under certain regulations; but it was not enjoined, Moses merely suffered it, because of the hardness of their hearts, as our Lord justly remarks Mat 19:8.
The stubborn, rebellious, gluttonous, and drunken son is to be stoned to death - This law, severe as it may seem, must have acted as a powerful preventive of crime. If such a law were in force now, and duly executed, how many deaths of disobedient and profligate children would there be in all corners of the land!
His body shall not remain all night upon the tree - Its exposure for the space of one day was judged sufficient. The law which required this answered all the ends of public justice, exposed the shame and infamy of the conduct, but did not put to torture the feelings of humanity by requiring a perpetual exhibition of a human being, a slow prey to the most loathsome process of putrefaction. Did ever the spiking of the heads of state criminals prevent high treason? or the gibbeting of a thief or a murderer, prevent either murder or robbery? These questions may be safely answered in the negative; and the remains of the ancient barbarism which requires these disgusting and abominable exhibitions, and which are deplored by every feeling heart, should be banished with all possible speed. In the case given in the text, God considers the land as defiled while the body of the executed criminal lay exposed, hence it was enjoined, Thou shalt in any wise bury him that day.
For he that is hanged is accursed of God - That is, he has forfeited his life to the law; for it is written, Cursed is every one who continueth not in all things that are written in the book of the law to do them; and on his body, in the execution of the sentence of the law, the curse was considered as alighting; hence the necessity of removing the accursed thing out of sight. How excellent are all these laws! How wondrously well calculated to repress crimes by showing the enormity of sin! It is worthy of remark that in the infliction of punishment prescribed by the Mosaic law, we ever find that Mercy walks hand in hand with Judgment.