Deuteronomy 21:9

Deu 21:9. So shalt thou put away the guilt of innocent blood — Till this was done, the guilt was to be looked upon as national; but upon this being solemnly performed, the government was deemed to have done its duty, and the nation cleared of all guilt in this matter. No doubt the chief end of the appointment of this ceremony was to beget and preserve in the minds of men an abhorrence of murder, and a care to prevent or detect it.

Joseph Benson's Commentary on the Old and New Testaments (1811–1818) — public domain. Text from a community e-Sword module.

9. So shalt thou put away] Heb. and thou, thou shalt put away, an emphatic variation of the formula with which D usually closes similar laws (see Deu_13:5, (6), Deu_19:13, etc.), as if he only now resumed his own words.

when thou shalt do, etc.] To make the construction right we should prefix to this clause, the words that it may be well with thee. See Deu_6:18.

The Cambridge Bible for Schools and Colleges (gen. ed. J. J. S. Perowne; Cambridge University Press, 1878–1918) — public domain. Text from a community e-Sword module.

So shalt thou put away the guilt of innocent blood from among you,.... Which otherwise, the person not being found out, and brought to just punishment for it, would devolve upon the whole. Aben Ezra interprets it the punishment of innocent blood, which, by the above method being taken, would not be inflicted on them:

when thou shalt do that which is right in the sight of the Lord; as it was to observe this law concerning the beheading of the heifer, with all the rites and ceremonies belonging to it here enjoined; as well as every other command, statute, and ordinance of the Lord, which are all right to be done, Psa 19:8.

John Gill's Exposition of the Whole Bible (1746–1763) — public domain (CC PDM 1.0). Text via the HelloAO Bible API.

And, &c. Hebrew, "Thou shalt put away," (Haydock) or "extinguish the voice of innocent blood," which otherwise would cry to heaven for vengeance, Genesis iv. 10. In this sacrifice, (Calmet) though it deserves not the name, (Menochius) we may consider Jesus Christ suffering for the sins of others. (Calmet)

George Leo Haydock (1774–1849), Haydock's Catholic Family Bible and Commentary, 1859 edition — public domain. Excludes Psalms (Douay-Rheims chapter numbering differs from Protestant) and Deuterocanonical books (Catholic canon only).

In this way they were to deliver themselves as a nation from blood-guiltiness. "Expiation was made by the killing of the transgressor when he could be found (Deu_19:13; Num_35:33) when he was not known, by the process here described. Of course, if afterwards he were apprehended, he would suffer the penalty he had incurred" (Knobel); so also Keil, Herxheimer, etc., after the Talmud ("Sota," 9:7).

The Pulpit Commentary (1880–1919), ed. H.D.M. Spence-Jones & Joseph S. Exell — public domain. Text from a community e-Sword module.

ואתה תבער BUT THOU SHALT PUT AWAY [THE GUILT OF INNOCENT BLOOD FROM AMONG YOU] — This teaches that if the murderer is found after the heifer’s neck was broken he must nevertheless be put to death, — and this is what Scripture describes as הישר בעיני ה׳ RIGHT IN THE EYES OF THE LORD (cf. Sotah 47b; Ketubot 37b and Tosafot on Ketubot 37b:16.1 ואח"כ נמצא ההורג).

Rashi on the Tanakh — English translations: “The Judaica Press complete Tanach with Rashi, translated by A. J. Rosenberg” (CC BY 4.0); “Pentateuch with Rashi's commentary by M. Rosenbaum and A.M. Silbermann, 1929-1934” (public domain); “The Metsudah Tanach series, Lakewood, N.J” (CC BY 4.0); and “The Book of Joshua, Metsudah Publications, 1997” (CC BY 4.0). Text via Sefaria.