והנה מצות התשובה מן התורה היא עזיבת החטא בלבד
Now the mitzvah of repentance1 as required by the Torah is simply the abandonment of sin
כדאיתא בגמרא ,פרק ג׳ דסנהדרין, ובחושן משפט, סוף סימן ל״ד, לענין עדות
(2cf. Sanhedrin, ch. 33; Choshen Mishpat, end of Sec. 34,4 regarding testimony5), where it is stated that if a potential witness simply abandons and does not repeat the transgression that had previously disqualified him, he is once again able to testify.6
דהיינו שיגמור בלבו בלב שלם לבל ישוב עוד לכסלה, למרוד במלכותו יתברך
This means that he must resolve in perfect sincerity never again to revert to folly, to rebel against G‑d's rule;
ולא יעבור עוד מצות המלך, חס ושלום, הן במצות עשה הן במצות לא תעשה
he will never again violate the King's command, G‑d forbid, neither a positive command7 nor a prohibition.8
וזהו עיקר פירוש לשון תשובה: לשוב אל ה׳ בכל לבו ובכל נפשו, לעבדו ולשמור כל מצותיו
This is the basic meaning of the term teshuvah ("repentance") — to return to G‑d with all one's heart and soul, to serve Him, and to observe all His commandments.
כמו שכתוב: יעזוב רשע דרכו ואיש און מחשבותיו, וישוב אל ה׳ וגו׳
For so does Scripture state:9 "Let the wicked abandon his path, and the sinful his thoughts, and return to G‑d…."
ובפרשת נצבים כתיב: ושבת עד ה׳ אלקיך ושמעת בקולו וגו׳ בכל לבבך וגו׳
In the Torah portion of Nitzavim10 it is likewise written:11 "You shall return unto the Lord your G‑d and hearken to His voice…with all your heart…."12
שובה ישראל עד ה׳ אלקיך וגו׳, השיבנו ה׳ אליך וגו׳
[So, too:]13 "Return, O Israel, unto the L‑rd your G‑d..."; [and elsewhere:]14 "Bring us back, O L‑rd, unto You…."
Repentance, then, entails returning to G‑d, performing his commandments and refraining from sin.
ולא כדעת ההמון שהתשובה היא התענית
This differs from the popular conception that repentance is synonymous with fasting on account of one's sins.
ואפילו מי שעבר על כריתות ומיתות בית דין, שגמר כפרתו היא על ידי יסורים
Even in the case of sins punishable by excision or execution, where atonement is made complete by suffering, as previously quoted from the Beraita in Yoma,
היינו שהקב״ה מביא עליו יסורים
this means that it is G‑d Who brings suffering upon the sinner, in order to complete his atonement.
וכמו שכתוב: ופקדתי בשבט וגו׳, ופקדתי דייקא
(15as the verse clearly specifies, "With a rod shall I remember [their sin]").
והיינו: כשתשובתו רצויה לפניו יתברך, בשובו אל ה׳ בכל לבו ונפשו מאהבה
That is to say: When G‑d finds his repentance acceptable, as he returns to Him with all his heart and soul, out of love,
אזי באתערותא דלתתא וכמים הפנים וכו׳, אתערותא דלעילא, לעורר האהבה וחסד ה׳ למרק עונו ביסורים בעולם הזה
then following the initiative undertaken from below, and16 "as water reflects the countenance...," there is an awakening Above, arousing G‑d's love and kindness, to scour his sin and entirely cleanse him of it through affliction in This World,
וכמו שכתוב: כי את אשר יאהב ה׳ יוכיח
in the spirit of the verse,17 "For he whom the L‑rd loves He chastises…."
This is something quite different from any fasts or afflictions that an individual undertakes himself.
ולכן לא הזכירו הרמב״ם והסמ״ג שום תענית כלל במצות התשובה, אף בכריתות ומיתות בית דין
It is for this reason that the Rambam and Sefer Mitzvot Gadol18 make no mention whatever of fasting as related to the mitzvah of repentance, even in the case of sins punishable by excision or capital sins.
I.e., fasting is not required even with regard to those sins whose atonement is completed through suffering.
רק הוידוי ובקשת מחילה, כמו שכתוב בתורה: והתודו את חטאתם וגו׳
They cite only confessing [verbally] and requesting forgiveness; as the Torah prescribes,19 "They shall confess their sin…."
Why are confession and requesting forgiveness indeed part of repentance?
Every sin consists of a body and a soul. The actual misdeed itself is the "body" of the sin, and the bodily pleasure and ensuing desire with which it was committed are its "soul". Repentance involves eliminating both these elements.
The "soul" of the sin is eradicated by the earnest regret of the individual, who is mortified and pained by his past. Inasmuch as pain is the opposite of pleasure, it negates the pleasure which had earlier aroused his desire to sin, and thereby obliterates the "soul" of the sin.
But the "body" of the sin also needs to be nullified. Simply refraining from further transgression lacks the action that would negate the sinful act itself, its "body". This is accomplished through verbal confession, for20 "verbalization is also considered to be an action."
At any rate, verbal confession is thus a component of repentance — while fasting is not.
ומה שכתוב ביואל: שובו עדי בכל לבבכם, ובצום ובבכי גו׳
As to what we find in the Book of Yoel,21 "Return to Me with all your hearts, and with fasting and weeping...," which would seem to indicate that fasting is in fact part of return and repentance,
היינו לבטל הגזרה שנגזרה, למרק עון הדור על ידי יסורים בארבה
this was to nullify (Note inserted by the Rebbe: '…something which relates to the future, while repentance involves forsaking the past') the heavenly decree that had been issued, to expunge the sin of the generation through the affliction of locusts; it was not part of the act of repentance.
וזהו הטעם בכל תעניות שמתענין על כל צרה שלא תבא על הצבור
This is the rationale for all fasts undertaken for any trouble threatening the community, their purpose being to avert the impending harsh edict,
וכמו שכתוב במגלת אסתר
as in the Book of Esther,22 where we find that the Queen asked that a fast be proclaimed in order to nullify Haman's evil decree.
ומה שכתוב בספרי המוסר, ובראשם ספר הרוקח וספר חסידים, הרבה תעניות וסיגופים לעובר על כריתות ומיתות בית דין
Now the classic Mussar works, particularly the Rokeach and Sefer Chassidim, specify numerous fasts and mortifications23 for sins punishable by excision and execution;
וכן למוציא זרע לבטלה, שחייב מיתה בידי שמים, כמו שכתוב בתורה גבי ער ועונן
likewise numerous fasts are prescribed for the wasteful emission of semen — a sin punishable by death by divine agency, as the Torah recounts of Er and Onan,24
ודינן כחייבי כריתות לענין זה
and a sin whose retribution is identical in this respect to that of sins punishable by excision, and hence the numerous fasts prescribed.
All this might lead us to assume that the purpose of fasts is suffering — this being the manner through which atonement is brought to completion by those who are guilty of sins punishable by excision. But it has been previously stated that the suffering which completes atonement is specifically that which comes from Above, and not manmade suffering incurred through fasting and the like. The Alter Rebbe answers this seeming contradiction by stating:
היינו: כדי לינצל מעונש יסורים של מעלה, חס ושלום
These above-prescribed fasts and mortifications are intended to avert the punishment of suffering at the hand of heaven, G‑d forbid. (Note of the Rebbe: "This too relates to the future, unlike repentance, which relates to the past.")
This means that if, G‑d forbid, the punishment of suffering had been decreed upon an individual, he is able to exempt himself from it through these self-imposed fasts.
וגם כדי לזרז ולמהר גמר כפרת נפשו
Another reason [for these fasts] is to urge on and expedite the conclusion of his soul's atonement.
וגם אולי אינו שב אל ה׳ בכל לבו ונפשו מאהבה, כי אם מיראה
Also, perhaps he is not returning to G‑d with all his heart and soul out of love, but only out of fear.
Such a penitent would not enjoy the Divine reaction that comes "as water reflects the countenance," and would not be granted the completion of his atonement through suffering. Accordingly, he might undertake these fasts in order to secure this alone. Essentially, however, the suffering that brings about complete atonement (for those guilty of sins punishable by excision and death by Divine agency) is not meant to be self-inflicted, but rather — heaven forfend — imposed from Above.