The Alter Rebbe explained in the previous chapter that although a penitent should always remember his past sins, his recollection should not lead to a state of ongoing depression or shame; such an attitude would cripple the cardinal principle of serving G‑d with joy. Rather, he should recall his past misdeeds “from afar” — only insofar as they will teach him to be humble before all men.

Moreover, these memories will actually enhance the joy of his Divine service, for they will cause him to accept with happy equanimity all manner of pain and suffering, be it verbal or physical, whether visited upon him from Above or through mortal agents.

In this, the concluding chapter of Iggeret HaTeshuvah, the Alter Rebbe explains why these afflictions cause the penitent joy.

וטעם השמחה ביסורי הגוף

The reason for joy1 in the suffering of the body

לפי שהיא טובה גדולה ועצומה לנפש החוטאת

is that it is a great and potent2 favor for the sinning soul,

למרקה בעולם הזה

to cleanse it in This World,3

ולהצילה מהמירוק בגיהנם

and to spare it from being scoured in Gehinnom.4

(בפרט בדורותינו אלה

(5This is particularly true in these generations of ours,

שאין ביכולת להתענות כפי מספר כל הצומות שבתיקוני תשובה מהאריז"ל

when one cannot undertake all the fasts prescribed in the penances of the AriZal, as mentioned earlier on in chapter 3,

הצריכות למירוק הנפש, להצילה ממירוק בגיהנם)

fasts imperative for the cleansing of the soul, to rescue it from the cleansing of Gehinnom.)

וכמו שכתוב הרמב"ן ז"ל בהקדמה לפירוש לאיוב, שאפילו יסורים של איוב ע' שנה, אין להן ערך כלל ליסורי הנפש שעה אחת בגיהנם

As Nachmanides writes, in the Introduction to his Commentary on Job, that even the sufferings of Job for seventy years bear absolutely no comparison to the suffering of a soul for even one hour in Gehinnom,

כי אש אחד מששים וכו'

for6 “[physical] fire is but one sixtieth [of the fire of Gehinnom].”

אלא לפי שעולם הזה חסד יבנה

It is only that this7 “world is built by kindness,”

וביסורין קלין בעולם הזה, ניצול מדינים קשים של עולם הבא

for which reason through mild suffering in This World one is saved from severe judgments in the Coming World.

כמשל הילוך והעתקת הצל בארץ טפח

This is analogous to the movement of a shadow on earth of a handsbreadth,

לפי הילוך גלגל השמש ברקיע אלפים מילין וכו'

which equals the sun's movement in the heaven of thousands of miles…

I.e., the sun's movement of thousands of miles causes a corresponding movement of but a few inches of shadow].

ויתר על כן לאין קץ הוא בנמשל

Infinitely more so is this true in the parallel,

בבחינת השתלשלות העולמות מרום המעלות עד עולם הזה הגשמי

in the descent of the worlds from level to level, from the most exalted heights until this physical world.

The analogy may be understood as follows. Any event that transpires in this world results from a parallel but far more ethereal event that “previously” took place in the spiritually exalted worlds. Thus, the effect of an event in this physical world is much greater in those lofty worlds.

וכנודע ממה שכתוב בזהר הקדוש, מענין עליות עולמות העליונים

We see this in the teachings of the Zohar on the elevation of the higher worlds

באתערותא דלתתא, בהקרבת עוף אחד בן יונה או תור על גבי המזבח, או קומץ מנחה

as a result of the spiritual arousal initiated by man below through his offering of one fowl, a dove or pigeon, or a handful of meal, on the altar.

The Zohar teaches that offering but one such representative creature from the animal world or but one such representative item from the vegetative world, elevates all the spiritual realms.

וכן הוא בכל המצות מעשיות, כנודע מהאריז"ל

Such are the effects of all the commandments requiring practical performance, as is known from the AriZal.

Mitzvot performed in this world with physical objects, such as tzitzit made of wool or the passages of the tefillin written on parchment, set up far-reaching reverberations in the exalted spiritual worlds.

וזהו שאמרו רז"ל על פסוק: והתקדשתם והייתם קדושים

This too is our Sages' comment8 on the verse,9 “Sanctify yourselves and you shall be holy” —

אדם מקדש עצמו מעט מלמטה, מקדשין אותו הרבה מלמעלה וכו'

“Man sanctifies himself [only] a little i.e.,” comments the Rebbe, ‘in quantity’ below i.e.,“ comments the Rebbe, ‘in quality’, and he becomes sanctified in great measure from Above…”

(וכמו שכתוב לעיל בענין אשר קדשנו במצותיו וכו' בחינת סובב כל עלמין וכו')

(10It was thus noted above11 in reference to the phrase, “Who sanctified us with His commandments…,” [that Israel's sanctification through mitzvot is bound up with the Infinite life- force that] encompasses and transcends all worlds…)

Thus, the physical performance of a Divine commandment in this world, draws down upon the individual holiness not only from the most lofty spiritual worlds, but also from the degree of G‑dliness that transcends worlds.

וככה ממש הוא בענין שכר ועונש

Precisely so is it in reference to reward and punishment.

The reward for the performance of a mitzvah infinitely surpasses the physical deed itself; the punishment as well, suffered by an individual in this world for his sins, substitutes for a far greater measure of punishment that the person would have undergone had it been meted out in the Coming World.

כמאמר רז"ל: שכר מצוה מצוה וכו'

As our Sages say,12 “The reward of a mitzvah is the mitzvah…”;

[I.e., the reward is the spiritual illumination that is drawn down through the fulfillment of the mitzvah itself],

וכמו שכתוב במקום אחר

as discussed elsewhere.

Since it has just been explained that the performance of a mitzvah draws down as a reward Divine illumination that utterly transcends all worlds, it follows that the reward for the mitzvah in the loftier spiritual worlds is infinitely higher than the physical action performed here below.

ודעת לנבון נקל

This knowledge is elementary to the discerning,

ומשכיל על דבר ימצא טוב

and those with intelligence in this matter will discover good.