The above discussion relates only to the drawing down of Divine vitality from the Shechinah into the created worlds, which parallels the emanation of the spirit of life from the heart and its diffusion throughout the entire body.
The Alter Rebbe will now go on to explain the second aspect of this analogy — how the spirit of life returns to the heart from the other organs. In the analogue likewise, the G‑dly life-force within the worlds pulsates in an ongoing dual dynamic called ratzo vashov (“advance and retreat”): the G‑dly life-force is first drawn downward, from the Shechinah to the worlds, and then it returns to its source, as a result of the Torah study and the spiritual service of created beings.
ונודע בשערים
And it is well known at the gates13
כי כל המשכת החיות וההשפעה מעליונים לתחתונים מהם
that every downflow of [Divine] life-force and [all] effluence from the upper worlds to the worlds which are lower than them,
הן כמו שכתוב בספר יצירה: נעוץ תחלתן בסופן, וסופן בתחלתן
are as stated in the Sefer Yetzirah:14 “Their beginning (i.e., the beginning of the uppermost levels of creation) is wedged in their culmination (i.e., in the nethermost part of the lowest level of creation), and their culmination is wedged in their beginning.”
ובכתבי האריז״ל, מכונה בשם אור ישר ואור חוזר
In the writings of R. Isaac Luria, of blessed memory, this [dual direction] is referred to as Or Yashar (“direct light”) and Or Chozer (“reflected light”), i.e., light reflected upwards from the lower level back to the upper;
וכמו שכתוב: והחיות רצוא ושוב
as it is also written,15 “And the Chayot were advancing and retreating,” first proceeding away from their Source and then retreating to it.
The above verse refers to the holy Chayot (“creatures”) of the Divine Chariot. The Kabbalah explains that this is an allusion to the Divine life-force of all worlds and created beings: it first emanates from its Source and then returns to it. I.e., not only is the Divine life-force drawn from the Shechinah down into creation, but it also returns from created beings back to its original Source.
אשר על כן, על פי הדברים והאמת האלה, אשר אי אפשר לבאר היטב במכתב
Thus, according to these words and this truth, which is impossible to explain properly in writing,
נקראת השכינה בשם לב, והנשמות בשם אברים
the Shechinah is referred to as the “heart”, and the souls as “organs”.
להורות לנו, כי כאשר כל הנשמות דבוקות ומקושרות יחד
This teaches us that when all the souls are attached and bound together,
אזי סיבוב והילוך החיות וההשפעה סובב סובב
the circulation and flow of the life-force and of the effluence from the Shechinah to the worlds and from the worlds back to the Shechinah is continuous,
ונעוץ סופן בתחלתן, לקשר ולחבר כולן להוי׳ אחד, ולדבקה בו יתברך
and “their culmination is wedged in their beginning,” thus binding and joining them all — all the souls, and through them all the worlds — to the One G‑d, so that they will cleave to Him.
וכמו שכתוב: אתם נצבים היום כולכם לפני הוי׳ אלקיכם
Thus it is written,16 “You are standing firm this day, all of you, before the L‑rd your G‑d (Havayah Elokeichem).”
כולכם דייקא, ולפני דייקא
The verse specifies “all of you,” i.e., a situation in which all Jews stand united together. Moreover, it specifies “before”, implying that this togetherness enables all Jews to relate to Divinity at the level at which the Name Havayah precedes and transcends its subsequent self-imposed descent to become Elokeichem, the life-force that empowers souls.
This can take place only when there is a sense of unity between all the levels which the above verse goes on to enumerate:
ראשיכם כו׳ מחוטב עציך כו׳
“Your heads…” (i.e, those with the loftiest souls), “from the hewer of your wood…” (i.e., those of more modest spiritual stature).
The Alter Rebbe elaborates on this unity between unequals in Likkutei Torah, at the beginning of Parshat Nitzavim.
ובזה יובן מאמר רז״ל, כי חורבן בית שני ונפילת ישראל בגלות
This will clarify the teaching of our Sages,17 of blessed memory, that the destruction of the Second Temple and the fall of Israel into exile,
והסתלקות השכינה וירידתה לאדום, בבחינת גלות, כביכול
and the withdrawal of the Shechinah and its descent to Edom, into a state of exile, as it were, for when the Jews are exiled, so too is the Shechinah,18
הכל היה בעון שנאת חנם ופירוד לבבות, רחמנא ליצלן
— all this was because of the sin of groundless hatred [between one Jew and another] and dissension between their hearts (May the Merciful One save us!).
ולכן נקראת חולה, על דרך משל
And this is why [the Shechinah] is referred to metaphorically as ailing (in times of exile, as quoted above).
ומה שכתוב: סומך נופלים ורופא חולים, לשון רבים
As for19 the phrases [in the Amidah], “He supports those who are fallen and heals those who are sick,” in plural form — although reference is being made to the Shechinah,
הם כל האברים וכו׳
this alludes to all the organs….
The plural form includes the souls which are the “organs of the Shechinah,” inasmuch as they are animated by it; they, too, are in ailing health, and they, too, are supported and healed.