The foundational Talmudic debate originates in Yoma 85b, where the Gemara notes that the Mishnah conditions atonement on repentance — "with repentance, yes; by themselves, without repentance, no" — but then surfaces Rabbi Yehuda HaNasi's dissenting view that Yom Kippur atones for all transgressions whether or not one repented, excepting only the gravest categories such as rejecting the yoke of Torah, denying God, and violating the covenant of circumcision, for which repentance remains indispensable even according to Rabbi.
The Gemara in Yoma 86a and Yalkut Shimoni on Torah 295:1 develop the graduated structure of atonement according to the Sages: a positive commandment is forgiven immediately upon repentance; a prohibition requires repentance to suspend punishment while Yom Kippur completes the atonement; and for transgressions carrying karet or court-imposed death, both repentance and Yom Kippur together only suspend, while suffering then purges — a scheme in which repentance is required at every tier.
The pasuk cited throughout as the textual basis for Yom Kippur's atoning power, Vayikra 23:28, declares "for it is Yom Kippur, to atone for you before the Lord your God," and Pirkei DeRabbi Eliezer 46:7 reads the phrase "from all your sins" (מִכֹּל חַטֹּאתֵיכֶם) expansively, suggesting the day atones for both light and severe transgressions, while the Sforno (Vayikra 16:30) understands the priestly service as diminishing the sin and preparing it to receive forgiveness.
The Rambam rules in Mishneh Torah, Repentance 1:3 that "the essence of Yom Kippur atones for those who return" (לַשָּׁבִים), and the Kessef Mishneh (Mishneh Torah, Repentance 1:3) explains explicitly that this formulation reflects the Rambam's rejection of Rabbi's view: since we do not rule like Rabbi against the majority, the Rambam's phrase "for those who return" deliberately excludes those who have not repented; and Mishneh Torah, Repentance 1:4 reinforces this by listing the specific categories where teshuvah suspends and Yom Kippur completes atonement, in every case presupposing repentance.
The Rambam further emphasizes in Mishneh Torah, Repentance 2:7 that Yom Kippur is the appointed time of repentance for all — individual and community — and the seal of forgiveness for Israel, making teshuvah and vidui on the day an obligation, while Sefer HaChinukh 364:5 similarly stresses that one who passes Yom Kippur without confessing has forfeited the day's atonement, and Shulchan Arukh, Orach Chayim 607:6 adds that Yom Kippur atones only for "those who return and believe in its atonement," explicitly excluding one who internally dismisses the day.
The question of what עיצומו של יום (the day's own essence) accomplishes without repentance is pressed sharply by מכתב מאליהו, חלק א יום הכפורים, עמוד רסד, וראה שם עוד, which notes that even though we rule that Yom Kippur requires teshuvah, the Rambam still invokes the phrase "the essence of the day atones" — citing the Kessef Mishneh's gloss that this means together with repentance — and presses the conceptual difficulty: atonement without any repentance would be like immersing in a mikveh while holding an impurity, and the passage asks what the category of עיצומו של יום adds once the person has already repented.
Resisei Layla 54:4 offers a mystical grounding for why Yom Kippur's atonement reaches even those who have not repented: God's knowledge that Israel's true inner will is to fulfill His will, and that sins arise only from the "leaven in the dough" and the burden of exile, renders the sins analogous to thorns surrounding the myrtle — the core remains pure — so atonement flows from the eternal bond between God and Israel rather than from any act of the individual.
The Rebbe's maamar in Maamarim Melukatim, ש"פ האזינו, שבת תשובה ה'תשכ"ג explains, on our reading of the cited page, that the revelation accomplished through the High Priest's entry into the Holy of Holies operates at a level above the chain of descent — comparable to the eighth day of circumcision — and that both teshuvah and kapparah draw their power from this transcendent dimension, grounding the capacity for atonement in something beyond the ordinary calculus of sin and repentance; and Maamarim Melukatim, ש"פ האזינו, שבת תשובה, ה'תשל"ו addresses, on our reading of the cited page, the layered articulation of teshuvah in the Shabbat Teshuvah Haftarah, exploring why the call is to "Israel" — the elevated name — rather than "Jacob," and the multiple distinct levels implied by the sequential phrases of the passage.
Peninei Halakhah, Days of Awe 6:8 articulates Rabbi's position directly: Yom Kippur's fundamental atonement extends to every individual Israelite even if he did not repent, even if he desecrated the day by eating or working, because the atonement is a divine decision rooted in the eternal bond between God and Israel — and accordingly, even one who declares he does not want Yom Kippur to atone for him is atoned for against his will; while Peninei Halakhah, Days of Awe 6:9 explains that according to the Sages, the day does not rescue the individual who has not repented from the judgment his sins warrant, though even they do not require complete repentance in the fullest sense — fasting, refraining from labor, and prayer suffice to reveal one's inner will to be good, and that inner will is what activates the day's protection.
Tanya, Part I; Likkutei Amarim 29:13 teaches that teshuvah is essentially a matter of the heart and has many gradations and levels depending on the person, the time, and the place; if the light of the soul does not penetrate after repentance, this signals either that the repentance was not yet accepted or that one is being summoned to a yet deeper level of teshuvah — a framework that implies the work of repentance is never mechanically complete and must continually deepen, while Tanya, Part I; Likkutei Amarim 29:5 locates the obstacle in the coarseness of the kelipah, which rises against the light of the divine soul and obscures it.
Minchas Yitzchak (Minchas Yitzchak 7:40) opens with the Mishnah's ruling that one who says "I will sin and Yom Kippur will atone" is not given the opportunity to repent, and on our reading of the full cited page, he analyzes this in light of the dispute over whether עיצומו של יום מכפר without repentance, examining Rabbi's position against that of the Sages and how the Rambam codifies these principles in Hilchos Teshuvah.
Igros Moshe (Igros Moshe OC 4:119) addresses the Tosafot's question on Shavuot 13a — why the Sifra derives that Yom Kippur atones in all circumstances ("מכל מקום") even without repentance and even if one did not treat the day as holy — and on our reading of the full cited page, Rav Moshe Feinstein resolves the difficulties raised by Tosafot and explains the scope of that derivation.