Let us elucidate further the term "to do it." Let us also understand, in a very small measure, the purpose of the creation of "Intermediates" and the descent of their souls into this world, to be clothed within he animal soul which is derived from the kelipah and sitra achra. Since they will not be able to banish her [the animal soul] throughout their lives, nor to dislodge her from her place in the left part of the heart, so that none of her impure fancies should rise to the brain, inasmuch as the very essence of the animal soul derived from the kelipah remains [in the Intermediates] in her full strength and might as at birth, except that her "garments" do not invest their bodies, as discussed above— if so, why have their souls descended into this world to labour in vain, G‑d forbid, to wage war throughout their lives against the [evil] nature which they cannot vanquish?

But let this be their solace, to comfort them doubly and helpfully, and to gladden their heart in G‑d, Who dwells with them in their Torah and [Divine] Service:

To quote, by way of preface, the comment of the Yenuka (Zohar, Parshat Balak) on the verse: "The wise man's eyes are in his head": "Where else are a man's eyes? ... But the interpretation of the verse certainly is as follows: We have learned that a man must not walk four cubits bareheaded. The reason is that the Shechinah rests on his head; and a wise man's eyes and everything he possesses are 'in his head,' i.e. in Him Who rests and abides above his head; and if his eyes are there, he must know that the Light which shines above his head needs oil; for the body of a man is a wick, and the Light is kindled above it. And King Solomon cried, saying, 'Let there be no lack of oil above thy head.' For the Light on a man's head must have oil, meaning good deeds, and this is the meaning of the phrase, 'The wise man's eyes are in his head.'" The quotation ends here.

The explanation of this figure, whereby the Light of the Shechinah is compared to the flame of a lamp which produces no light nor clings to the wick without oil, and likewise the Shechinah does not rest on a man’s body, which is likened to a wick, except through good deeds alone, and it is not sufficient that his soul (neshamah), which is a part of G‑dliness from above, should act for him as oil to the wick—is clear and understandable to every intelligent person.

It is, that the neshamah of a person—even if he be a perfect tzaddik serving G‑d with fear and love of delights—does not, nevertheless, completely dissolve itself out of existence, so as to be truly nullified and absorbed into the light of G‑d to the extent of becoming one and the same absolutely, but the person remains an entity apart, one who fears G‑d and loves Him. It is different, however, with the commandments and good deeds, which are His blessed will. His blessed will is the source of life for all the worlds and creatures, flowing down to them through the many contractions (tzimtzumim) and the concealment of the countenance of the Supreme Will (Ratzon Elyon), blessed be He, and the recession of the levels, until it was made possible for creatures to come into being ex nihilo, separate beings that should not lose their identity, as discussed above. The commandments, however, are different in that they are the inwardness of His blessed will, without any concealment of the countenance whatever; the vitality that is in them [therefore] is in no way a separate being, but is united and absorbed in His blessed will, and they become truly one with a perfect union.

Now, the meaning of the "indwelling" of the Shechinah is the revelation of His blessed Divinity and of the light of the blessed En Sof in anything. That is to say, that such thing merges into the light of G‑d, and its reality is completely dissolved in Him; only then does the One G‑d abide and manifest Himself in it. But any thing whose reality is not completely nullified in Him, the light of G‑d does not abide nor manifest itself therein, even if one be a perfect tzaddik who cleaves to Him with abundant love, since no thought can truly apprehend Him at all. For the truth of "The Lord is the true G‑d" is His Unity and Oneness— that He is One Alone and there is no reality whatsoever apart from Him. Hence the person who loves [G‑d] and [ipso facto] exists [apart] and is not null and void— cannot by his thought apprehend Him at all; and the light of G‑d cannot abide and reveal itself in him, except through the fulfillment of the commandments which constitute in reality His blessed will and wisdom without any concealment of Countenance.

Note: This accords with the comment and explanation which I heard from my teacher, peace to him, on a passage in Etz Chayim stating that the light of the blessed En Sof does not become unified even in the world of Atzilut, unless it clothes itself first in the sefirah of Wisdomthe reason being that the Messed En Sof is the true One Who is One Alone and apart from Whom there is nothing, and this is the level of Wisdom, and so on.

Therefore, when a person occupies himself in the Torah, his neshamah, which is his divine soul, with her two innermost garments only, namely the power of speech and thought, are absorbed in the Divine light of the blessed En Sof, and are united with it in a perfect union. This constitutes the resting of the Shechinah on his divine soul, as the Rabbis stated, "Even if one person sedulously occupies himself with the Torah, the Shechinah is with him."

However, in order to draw the light and effulgence of the Shechinah also over his body and animal soul, i.e. on the vital spirit clothed in the physical body, he needs to fulfil the practical commandments which are performed by the body itself. For then the very energy of the body itself which is engaged in this action is absorbed in the Divine light and in His will, and is united with Him in a perfect union. This is the third garment of the divine soul. Thereby also the energy of the vital spirit in the physical body, originating in the kelipat nogah, is transformed from evil to good, and is actually absorbed into holiness like the divine soul itself, since it is this [animal soul] that carries out and performs the act of the commandment, because without it the divine soul could not have been acting through the body at all, for it is spiritual whilst the body is material and coarse. The intermediary linking them is the vital animal soul, which is clothed in the human blood, in the heart and in all the body.

And although the essence and substance of the animal soul in his heart, namely its evil dispositions, have not yet been absorbed into holiness, nevertheless since they have submitted to holiness and, albeit unwillingly, respond "Amen" and agree and are reconciled to perform the commandment, under the preponderance of the divine soul in his brain which rules the heart, and, in the meantime, these [evil dispositions] are in a state of exile or slumber, as it were, as discussed above— therefore, this is no obstacle to the suffusion of the Shechinah over the human body at such time. Thus the energy of the vital soul that is embodied in the performance of the commandment is actually absorbed into the Divine light and is united with it in a perfect union, thereby illuminating the totality of the vital soul throughout the body, and also the physical body itself in a manner of "Encompassing from above," from head to foot. This is what is meant by the phrase, "The Shechinah rests on his head; the word "on" indicates this. Similarly, "On every [assembly of] ten the Shechinah rests."

Clearly, any such diffusion of the light of the Shechinah, that is the revelation of the light of the blessed En Sof, cannot be termed mutability in Him, G‑d forbid, nor multiplicity. Witness the passage in Stair hedrin, where a heretic said to Rabban Gamliel: "You say that on every assembly often men the Shechinah rests. How many Divine Presences have you, then?" And he replied to him with an example of the light of the sun which enters through many windows.... The intelligent man will understand.