In other words, when Hashem gave the Torah to the Jewish People, he made it possible for His Infinite Light to be fully invested and united with the Torah we learn and mitzvos we perform just like His Light is united with the His attributes in Atzilus.
As it is written, “And Hashem descended onto Mount Sinai,” (Shemos, 19:20). וּכְמו ש כָּּתוּב (יִּתְרו יט, כ) 'ה ד רֵּיַו": עַל הַר סִּינַי".
In other words, Hashem caused His Infinite Light to descend into our physical world by investing it into the Torah that we study with our physical brain and into the mitzvos we perform with our body. (So the idea of Hashem descending onto “Mount Sinai” was mainly about Him descending into the Torah and mitzvos that we received on Mount Sinai, not as much about the physical mountain per se.)
And about this, the sages said (Pesachim 68b) that: “It was this day [of the giving of the Torah] that caused Rav Yosef to become truly elevated,” as will be further explained in the maamar. וְעַל ז ה אָּמְרוּ דְּ "הַאי יו מָּא הוּא דְּ קָּא."םיִּרָּּג :
The maamar so far explained: There is a change to how the Torah and mitzvos were performed by Avraham and the forefathers before the Giving of the Torah, and how they are performed after: Before the Giving of the Torah, mitzvos only brought down Hashem’s Infinite Light in to the World of Atzilus which then “trickled down” into a greater revelation of Hashem in our world as well. After the Giving of the Torah, our mitzvos actually bring down Hashem’s Infinite Light into our physical world where this Light is invested in and united with every mitzvah just as it is invested in Hashem’s Attributes in Atzilus.
Note that the maamar started this paragraph by describing bringing Hashem’s Light into “wisdom” and “kindness” and then shifted to simply discuss “action based mitzvos.” Perhaps this is because the main revelation of His Light in our world is through the two all-encompassing mitzvos of Torah study and charity/acts of kindness, which together bring down His Light into our physical world (see Igeres Hakodesh ch. 5). However, in general, all the mitzvos that perform in action accomplish bringing down Hashem’s Infinite Light into our physical world.
