The Alter Rebbe will now point out that a careful reading of the passage from Ra’aya Mehemna reveals that it is not the laws themselves nor the study of them that are termed the Tree of Knowledge of Good and Evil. Rather, this term is applied to the actual food or other things which are prohibited or permitted, and which derive their life-force from kelipat nogah — for this is the Tree of Knowledge of Good and Evil, as will soon be explained.

אך באמת, כשתדקדק בלשון רעיא מהימנא דלעיל

But in truth, if you examine closely the above-quoted text of Ra’aya Mehemna —

ואילנא דטוב ורע, דאיהו איסור והיתר כו׳

“And the Tree of [Knowledge of] Good and Evil, i.e., prohibition and permission…” —

ולא אמר תורת איסור והיתר, או הלכות איסור והיתר

[you will note that] it does not say “the teachings (i.e., studying the subjects) of prohibition and permission,” nor “the laws of prohibition and permission,” which would suggest that they are (G‑d forbid) the Tree of Knowledge of Good and Evil.

אלא רצה לומר, דגוף דבר האסור והדבר המותר, הוא מאילנא דטוב ורע

Rather, it means to say that the actual thing which is prohibited, or the thing which is permitted, is of the Tree of Good and Evil,

שהוא קליפת נוגה, כמו שכתוב בעץ חיים

i.e., of kelipat nogah, as stated in Etz Chayim.47

וזהו לשון אסור, שהקליפה שורה עליו, ואינו יכול לעלות למעלה, כדבר המותר

This, in fact, is the root of “assur” (meaning “forbidden”; lit., “bound”): the kelipah hovers over [the forbidden thing] so that it cannot rise aloft to holiness like that which is “muttar” (meaning “permitted”; lit., “unbound”);

דהיינו, שאינו קשור ואסור בקליפה

[while “muttar”] means that [a permitted object] is not tied and bound (“assur”) to the kelipah that would anchor it,

ויוכל לעלות על ידי האדם האוכלו, בכוונה לה׳

and is [therefore] able to ascend by means of the person eating it with his mind on G‑d, e.g., in order to have the strength to serve Him.

וגם בסתם

The same applies when there is no specific intent,

כל אדם העובד ה׳, שבכח האכילה ההיא לומד ומתפלל לה׳

with any person who serves G‑d, who studies [Torah] and prays to G‑d with the energy derived from this eating,

ונמצא שנעשו אותיות התורה והתפלה העולה לה׳, מכח הנברר מהמאכל ההוא

so that the letters of Torah and of prayer which ascend to G‑d are formed out of the energy distilled from that food.

In other words, the life-force that derives from kelipat nogah is thereby elevated to G‑d.

וזהו בחול

This is so during the week: In order for the food eaten on weekdays to be elevated, it must be utilized for Torah or prayer.

אבל בשבת, שיש עליה לקליפת נוגה בעצמה, עם החיצוניות שבכל העולמות

But on the Sabbath, the kelipat nogah itself is elevated, together with the external aspect of all the worlds, for the Sabbath is characterized by the “elevation of the worlds” (aliyat haolamot).48

לכן מצוה לאכול כל תענוגים בשבת

It is therefore a mitzvah to eat all kinds of pleasurable things on the Sabbath, for the sake of oneg Shabbat (“enjoying the Sabbath”), irrespective of the fact that it gives one the strength to serve G‑d,

ולהרבות בבשר ויין

and to partake of more meat and wine than usual,

אף שבחול נקרא זולל וסובא

even though on a weekday one would be called a glutton and a drunkard.

מה שאין כן בדבר איסור

It is otherwise with a forbidden thing.

שאינו יכול לעלות, לא בשבת ולא בחול, גם כשמתפלל ולומד בכח ההוא

It cannot ascend [to holiness,] neither on the Sabbath nor on a weekday, even if one were to pray and study with that energy, i.e., with the energy derived from eating it49׳—

אם לא שאכל לפיקוח נפש, שהתירו רז״ל, ונעשה היתר גמור

unless one ate in order to save an endangered life, which is permitted by our Sages, of blessed memory, so that [the food] becomes [entirely]50 permissible.

Addendum

In the middle of the above Epistle, the Alter Rebbe stated that if “one ate [forbidden food] in order to save an endangered life,… [the food] becomes [entirely] permissible.”

The Rebbe notes95 that this concept is problematic; indeed, many editions of the Tanya omit the word “entirely”, which is evidently why it found its way into current editions as a bracketed text.

The Rebbe goes on to distinguish between prohibition (issur) and impurity (tumah). When something is prohibited, one can sense its inherent evil; for example, forbidden foods clog the mind and heart with spiritual congestion. Thus, even if a pregnant woman scented forbidden food on Yom Kippur and the Torah permitted her to eat it (if her life would otherwise be in danger),96 eating that food would still becloud her soul.

Moreover, even when the prohibition was not intrinsic to the food, but a thought or a statement invalidated it, as for example when an animal was slaughtered with idolatrous intent,97 eating this food leaves its imprint. Thus, for example, the Midrash98 traces the wayward path of Elisha ben Avuyah (known as “Acher”) to very early beginnings — before his birth his mother had tasted food that was prepared for idolatrous worship.

In light of the above, the Rebbe goes on to note, we can understand why a nursing mother who has eaten forbidden food, even when permitted to do so because her life was endangered, should refrain from nursing her child.99 For although eating this food was in fact halachically permitted, the nature of the food and the spiritual blemish which it imparts to her infant remain unchanged.

This is especially so, according to the halachic determination (with regard to one who is ill as well), that a life-threatening situation merely sets aside a prohibition; it does not make the prohibited object permissible.100

As the Rebbe concludes, the above considerations evidently explain why in current editions of Iggeret HaKodesh — regarding the food eaten in a life-threatening situation that becomes “[entirely] permissible” — the word “entirely” is bracket-ed, and in many editions never appeared.