There is a difference of opinion in the Gemara1 as to how atonement is achieved on Yom Kippur. The majority of the Sages are of the opinion that “Yom Kippur atones only for those who repent”; Rebbe (Rabbi Yehudah HaNasi) maintains that atonement is achieved on Yom Kippur “whether the person repents or not,” the reason being that “the very day [of Yom Kippur] brings atonement.” The halachic decision is rendered in favor of the Sages; in order for atonement to be achieved on Yom Kippur repentance must be present.2

The Sages do not dispute Rebbe’s point that “the very day brings atonement”; they agree that the individual’s penitence cannot possibly achieve the level of atonement accomplished by the day of Yom Kippur itself. Rather, the dispute centers around the manner in which one attains a state wherein “the very day brings about atonement.”

Rebbe maintains that as soon as Yom Kippur arrives, the sanctity of the day secures atonement for an individual’s sins, even if he fails to repent. The Sages, however, say that in order to achieve the atonement brought about through Yom Kippur, repentance is first necessary. Having repented, he can then realize the far loftier atonement that only the day of Yom Kippur can effect.

We can well understand how repentance rids the person of the taint of sin. For when a Jew repents and sincerely regrets his sins, he thereby expunges the pleasure he had experienced at the time he sinned. This, in turn, cleanses him from the evil that attached itself to him through his sin. However, how is it possible that a person’s sins are erased and eradicated simply because of the day of Yom Kippur?

A Jew’s attachment to G‑d exists on many levels. For example, a Jew is connected to G‑d by performing His commandments and by accepting upon himself the heavenly yoke; i.e., he is ready to do all that G‑d commands him.

There is also a deeper level of attachment, one that finds expression in repentance. If a Jew transgresses G‑d’s commands and throws off His heavenly yoke, he weakens his relationship with G‑d. Troubled by this, he repents.

Repentance emanates from a soul level that is more profound than that which motivates one to simply obey G‑d’s commands. As such, it has the ability to undo all the blemishes that were caused by the sins that had weakened his revealed relationship with G‑d. Hence, through repentance he achieves a higher degree of attachment.

However, the loftiest level of a Jew’s relationship with G‑d is that of the essential and intrinsic bond between the soul’s essence and G‑d’s Essence. Since the soul is truly a part of G‑d above, this bond knows no limitations and defies any form of expression, even so lofty an expression as that of repentance.

Just as this essential bond is beyond expression and cannot be improved upon through man’s Divine service, so, too, does it remain unaffected by man’s lack of service, or even by his sins. At this level of attachment, sins simply have no bearing.

On the day of Yom Kippur, this essential relationship with G‑d is revealed within every Jew, and then all sins are dissipated as a matter of course. The debate between the Sages and Rebbe is merely as to whether one must first repent in order for this level to be revealed; all, however, agree that once the level of Yom Kippur — “the day itself brings atonement” — is revealed, it accomplishes far more than does mere repentance.

Thus, concerning those levels within a man that are affected and blemished by sin, atonement must first be brought about by repentance, for repentance has the capacity to strengthen his bond with G‑d and nullify the sins that encumber his relationship with Him.

The atonement of Yom Kippur, however, results from the revelation in the Jew of the supreme level of relationship with G‑d; and at this level, sins lack the ability to blemish this relationship in any way. This is why Rebbe and the Sages are in perfect agreement that “the very day of Yom Kippur brings atonement.”

Based on Likkutei Sichos, Vol. IV, pp. 1149-1152.