“Consider a rasha/evil person that in some manner finds himself in Gan Eden, going and coming amongst the tzaddikim/just people that sear in the splendor of their crowns of glory, bathing themselves in the light of the Shechina. The tzaddikim experience there indescribable pleasures, while he suffers incommensurably. Completely unaccustomed to spirituality, for the rasha, this Gan Eden is an incomparable discomfort. As such, this is the essence of the makat choshech [‘the plague of darkness’]. And thus Moshe brought the darkness below, for he ‘extended his hand above the Heavens’ [Shemot 10:21] and Egypt fell in a darkness like never seen before” (the Slonimer Rebbe, Netivot Shalom, Parashat Bo).
The makat choshech meant a tzimtzum (“contraction and restriction”) of the light of Hashem and its physical manifestation. Truly, first a tzimtzum occurred at the spiritual level, in the degree of נטה ידך על-השמים Nete yadecha al’hashamayim, “Extend your hand to the Heaven” (Shemot 10:21), which was the command Hashem gave to Moshe to begin this plague on Egypt. And the ordinal gematria (mispar siduri, in the sofit version) of this pasuk is 166. This is the numerical value for the “regression” (i.e., the posterior/achorayim vision) of the Shem SaG (Name of Hashem spelled with 63 letters, being that the gematria of SaG equals 63). The Shem SaG is associated to Binah, and in man, it means the power of rational intellect. When the Holy Name is “regressed”, this indicates a diminishing or immaturity in the rational understanding – a state of contraction and restriction of the consciousness. In a level, the darkness indicates exactly the incapacity to see, hence rationally understand, resulting from the withdrawal of Divine light. Now, in the physical level, the material darkness is the actual result of this spiritual regression. This is the reason that immediately following the verse says, “That there may be darkness over the land of Egypt, even darkness which may be felt”. Now we can understand something more. For the talmid/student still distant from Torah, everything is strange, uncomfortable and devoid of meaning. The light of Torah, through the words of the rebbe/master, is so strong that the students close their eyes and hid themselves with fear from the great intensity of this Divine irradiation. Then, in this period, they still exist against a thick darkness, in a state of rational immaturity. With the eyes completed closed, they fear opening them to then experience the restrictive reality of their own (private) Egypt. In time and great patience from the master, as they begin opening their eyes so unaccustomed to see the spiritual truths, the light finally begins to enter them, at least to some degree. Finally, they begin perceiving that there is אור במושבתם Or bemoshvotam, “Light in their dwellings” (Shemot 10:23). In fact, the gematria of this verse with two for the kollel for each one of the two words being 999 – the equal gematria of the milui/expansion of the Holy Name Kel Shakai “G-d Almighty”, which refers to the level of “Creator of the world”*. Now, more illuminated, they can be cured and redeemed, and in this way begin revealing the aspect of Mashiach that exists in each and every one, G-d willing.
* The Sages note that the word shakai can be interpreted as meaning “He who [sha-] said ‘enough’ [-dai] for the expansion of the world, at the end of the week of creation” (Talmud, Chagigah 12a).