There is an additional aspect in the matter of forbidden foods. The reason they are called issur ["chained"] is that even in the case of one who has unwittingly eaten a forbidden food intending it to give him strength to serve G‑d by the energy of it, and he has, moreover, actually carried out his intention, having both studied and prayed with the energy of that food, nevertheless the vitality contained therein does not ascend and become clothed in the words of the Torah or prayer, as is the case with permitted foods, by reason of its being held captive in the power of the sitra achra of the three unclean kelipot. This is so even when the prohibition is a Rabbinic enactment, for the words of the Scribes are even more stringent than the words of .the Torah, and so forth.

Therefore, also the evil impulse (yetzer hara) and the force that strains after forbidden things is a demon of non-Jewish demons, which is the evil impulse of the nations whose souls are derived from the three unclean kelipot. On the other hand, the evil impulse and the craving force after permissible things to satisfy an appetite is a demon of the Jewish demons, tor it can be reverted to holiness, as is explained above. Nevertheless, before it has reverted to holiness it is sitra achra and kelipah, and even afterwards a trace of it remains attached to the body, since from each item of food and drink are immediately formed blood and flesh of his flesh. That is why the body must undergo the "Purgatory of the grave," in order to cleanse it and purify it of its uncleanness which it had received from the enjoyment of mundane things and pleasures, which are derived from the uncleanness of the kelipat nogah and of the Jewish demons; only one who had derived no enjoyment from this world all his life, as was the case with our Saintly Master [Rabbi Judah the Prince], is spared this.

As for innocent idle chatter, such as in the case of an ignoramus who cannot study, he must undergo a cleansing of his soul, to rid it of the uncleanness of this kelipah, through its being rolled in "The hollow of a sling," as is stated in the Zohar, Parshat Beshallach, p. 59. But with regard to forbidden speech, such as scoffing and slander and the like, which stem from the three completely unclean kelipot, the hollow of a sling (alone) does not suffice to cleanse and remove the uncleanness of the soul, but it must descend into Gehinnom [Purgatory].

So, too, he who is able to engage in the Torah, but occupies himself instead with frivolous things, the hollow of a sling cannot itself effectively scour and cleanse his soul, but severe penalties are meted out for neglect of the Torah in particular, apart from the general retribution for the neglect of a positive commandment through indolence, namely, in the Purgatory of Snow, as is explained elsewhere. Likewise, he who occupies himself with the sciences of the nations of the world is included among those who waste their time in profane matters, insofar as the sin of neglecting the Torah is concerned, as is explained in the Laws Concerning Study of the Torah. Moreover, the uncleanness of the science of the nations is greater than that of profane speech, for the latter informs and defiles only the middot which emanate from the element of the holy ruach within his divine soul with the contamination of the kelipat nogah that is contained in profane speech which is derived from the element of the evil ruach of this kelipah in his animal soul, as mentioned above; yet he does not defile the [intellectual] faculties of ChaBaD in his soul, for they are but words of foolishness and ignorance, since even fools and ignoramuses can speak that way. Not so in the case of the nations' science whereby he clothes and defiles the intellectual faculties of ChaBaD in his divine soul with the contamination of the kelipat nogah contained in those sciences, whither they have fallen through the "shattering of the vessels" out of the so-called "hinder part" of Chochmah of Kedushah, as is known to those familiar with the Esoteric Wisdom. Unless he employs [these sciences] as a useful instrument, viz., as a means of a more affluent livelihood to be able to serve G‑d, or knows how to apply them in the service of G‑d and His Torah. This is the reason why Maimonides and Nachmanides, of blessed memory, and their adherents, engaged in them.