During Elul and the Ten Days of Repentance, we use three different Hebrew words in asking G-d to forgive us: “selichah,” “mechilah,” and “kapparah.”
“Selichah” and its cognates appear close to 50 times in the Bible. Linguists connect it to the Akkadian “salahu” and the Aramaic “zelicha,” which mean “sprinkling.” Sprinkling blood on an altar is the main component of ritual sacrifices, which would explain why cognates of “selichah” appear numerous times in the context of sacrifices (e.g., Leviticus 4:20-35 and Leviticus 5:10-26).
“Selichah” also refers to a type of liturgical poem, or piyut, characterized by begging for forgiveness. These poems were originally recited in the Slach Lanu blessing of Shemonah Esrei, which is why they’re called selichot. Nowadays, of course, they’re recited before davening or after Shemonah Esrei.
“Mechilah” and its related forms do not appear anywhere in the Bible. It does, however, appear, as Rabbi Eliyahu HaBachur (1469-1549) notes, in rabbinic literature and traditional Jewish liturgy. In addition to designating forgiveness, “mechilah” also refers to canceling a debt or otherwise forgoing what one deserves.
Rabbi Moshe Meth (1551-1606) and Rabbi Yitzchak Eizik of Tirna (15th century) tie “mochel” to “mocheh” (wipe away). Rabbi Aharon Fuld (1791-1840), in his glosses to HaBachur, suggests that “mochel”/“mechilah” is derived from a portmanteau of “mocheh” and “al.”
Rabbi Moshe Yitzchak Avigdor (1801-1865) – who served as the chief rabbi of such Lithuanian communities as Slonim, Kovno, and Shkolv – and Rabbi Yehuda Aszad (1794-1866) write that “mechilah” is related to “yachel” (Numbers 30:3), which the Targum translates as cancel or nullify.
Rabbi Shlomo Pappenheim of Breslau (1740-1814) suggests a fascinating theory about Hebrew roots that is germane to the topic at hand. He proposes that many three-letter roots beginning with the letter mem are really derivatives of the remaining two letters of the word with the mem reversing their meaning. For example, “chok” means engrave, but “machak” means erase; “leitz” means scorn/mockery, but “meilitz” means justification/defense; “na” means movement, but “mana” means withholding; “rad” means governing/ruling, but “marad” means rebellion.
Although Rabbi Pappenheim doesn’t use this theory to explicate the meaning of “mechilah,” perhaps we can. The two-letter root of chet-lammed primarily refers to the creation of something hollow. Some familiar conjugations of this root include “challil” (flute), and “chillul” (desecration). In many cases, it refers to defiling/profaning something holy by emptying it of its holiness. When a Jew sins, he is essentially making himself a hollow vessel by emptying himself of his own holiness. Perhaps, then, “mechilah” is the mechanism by which G-d re-infuses the penitent sinner with holiness. It thus is the polar opposite of chet-lammed.
A third word for forgiveness is “kapparah.” The Malbim writes that some relate “kapparah” to “kofer”/“pidyon” (redeem or ransom). Kapparah involves paying a price that usually takes the form of a ritual sacrifice. Nowadays, many customarily perform a ritual on Erev Yom Kippur called kapparot in which one seeks atonement by giving a slaughtered chicken or alms to the poor.
Others explain, notes the Malbim, that “kapparah” is related to “kapporet” (cover). Kapparah is a form of forgiveness that covers up one’s sins, rendering them invisible. The sins, however, remain. We may harmonize these two approaches by noting that in English one “covers” one’s costs by offsetting the expenditure. Thus, covering and paying a price can be different facets of the same idea.
Rabbi Yaakov Tzvi Mecklenburg (1785-1865) writes that while selichah may be quantitatively stronger than mechilah, mechilah is qualitatively stronger than selichah. Selichah affects the entirety of one’s sin by delaying punishment to a later time. Mechilah, though, is qualitatively stronger because it can completely erase at least part of one’s sin.
Similarly, Rabbi Shlomo Aharon Wertheimer (1866-1935) writes that “selichah” refers to a temporary reprieve. The sinner is not punished for his misdeeds all at once; he is given time to slowly repay his debt. “Mechilah,” on the other hand, connotes immediate and complete forgiveness. Neither Rabbi Mecklenburg nor Rabbi Wertheimer address how these two terms differ from “kapparah.”
Rabbi Samson Raphael Hirsch (1808-1888) writes that “mechilah” denotes commuting the punishment that the guilty party deserves, “selichah” denotes correcting the relationship between the sinner and the one (or One) he sinned against, and “kapparah” denotes the total negation of any negative ramifications of the sin.