(From the book Shamati by Kabbalist Y. Ashlag)
Man is made of three bodies: A) The inner body, in which the holy soul is dressed. B) The Noga shell. C) The serpent’s skin. In order to save one from the two outer bodies, so that they do not interfere with the holy one, and in order for one to be able to use the inner body alone, one must contemplate solely on things related with the inner body. That means that one’s thought should always be occupied to the singular authority, meaning, “There is none else beside him”. That is He performs and will perform all deeds and that there is no creation in the world that can detach one from the sanctity. And because one refrains from thinking of those two bodies, they perish and die, as they have no nourishment and nothing to sustain them with, because the thoughts we think of them are their nourishment. Thus it is said: “in the sweat of thy face shalt thou eat bread” for before Man sinned, his livelihood did not depend upon the bread. That is he didn’t have to attract light and livelihood. But after the sin, when Man had been affixed to the serpent’s body, then life had been tied in with the bread, that is nourishment. Each time they (lights) must be attracted anew, and if they (the two bodies) are not nourished, they die. This had turned out to be a great correction, in order to be saved from those two bodies.
Thus one must try with all one’s might not to think thoughts that concern them (perhaps that’s what our sages meant when they said that to contemplate sin is worse than to commit it). Thought is their nourishment. That is the thoughts one thinks of them are what gives them life.
Thus one must think only of the inner body, for it is the dressing for the sacred soul. That means that one should think beyond one’s skin, which means not for one’s own benefit, but only of the good of the other, which is outside one’s skin. After one’s skin, there is no grip for the shells, for they hold only that which is within the body, which belongs to it. That means that anything that comes within the dressing of the body, they posses a hold of, whereas anything that is not dressed within the body, they cannot hold.
When one endures with thoughts that are beyond one’s skin, one attains what is called “though it be after my skin is torn from my body, I would see God” (Job 19, 26). That means that sanctity had been dressed within the body, while it was determined to work outside it, with no dressing whatsoever. The evil ones, however, who do want to work while light is dressed in the body, called within the skin, shall die without wisdom. For then they have no dressing of light, then they attain nothing. But only the righteous do attain the dressing of the light
within the body.