In the entire Chumash, the word "מוסר" - "Mussar" appears one time [Devarim 11-2].
וִֽידַעְתֶּם֮ הַיּוֹם֒ כִּ֣י׀ לֹ֣א אֶת־בְּנֵיכֶ֗ם אֲשֶׁ֤ר לֹֽא־יָדְעוּ֙ וַאֲשֶׁ֣ר לֹא־רָא֔וּ אֶת־מוּסַ֖ר יְהֹוָ֣ה אֱלֹהֵיכֶ֑ם אֶת־גׇּדְל֕וֹ אֶת־יָדוֹ֙ הַחֲזָקָ֔ה וּזְרֹע֖וֹ הַנְּטוּיָֽה׃
Know this day: for I don’t speak with your children who have not known, and who have not seen the chastisement of Hashem your God, his greatness, his mighty hand, and his outstretched arm.
Unkelos renders the word "אולפנא" - teaching, and in Targum Yerushalmi "אולפן אורייתא", teaching of the Torah. We see that מוסר means the Torah as Hashem teaches it, as the pasuk there says further [י"א ז]
"כי עיניכם הרואות"
"Because your eyes saw".
In other words, Torah as Hashem taught it - מוסר ה' א-להיכם. Mussar means understanding reality as it is and Torah is the perception of "עיניכם הרואות". [That is what Chazal mean when they say that at Sinai "שומעים את הנראה ורואים את הנשמע" as the Nefesh Hachaim (ש"ג פי"א) explains: ראייה - Perceiving reality as it is. שמיעה - perceiving the MEANING [משמעות] of reality. If so, רואים את הנשמע - what until then was just an idea, a concept, an understanding, they saw with their own eyes, as it was, with complete clarity. שומעין את הנראה - they heard what was normally seen, what they usually saw with clarity they now understood, with all its depth.]
The Rambam [ספר המצוות שורש ג] writes:
It is not fitting to count mitzvos that are not kept for all the generations. When Chazal say that "613 mitzvos were said to Moshe at Sinai" that is the number of mitzvos kept for all the generations. Because mitzvos that are not kept for the generations have no connection to Sinai. "At Sinai" because the עיקר of the Torah was given at Sinai.
We see from the Rambam that everything that happened at Sinai was for all the generations. This fits with what we explained earlier: At Sinai, as we explained, all of existence was transformed by the Torah. So of course Sinai relates to mitzvos that will apply for ALL the generations. Reality is a constant and thus what created that reality also relates to the constant i.e. mitzvos for all the generations and not the temporary ones.
The Rambam also says when listing his 13 principles of faith:
היסוד התשיעי - ההעתק, והוא כי התורה הזאת מועתקת מאת הבורא השם יתברך לא מזולתו. ועליה אין להוסיף וממנה אין לגרוע לא בתורה שבכתב ולא בתורה שבעל פה. שנאמר "לא תוסיף עליו ולא תגרע ממנו". |
This is the principle that Torah is eternal, it won't change and will last forever. The Rambam uses the terminology "העתקה" - copy. Since when the Torah is transmitted, it must be transmitted with "Sinai", therefore the transmission is a "העתקה" - a copy of Sinai. Thus, the Torah cannot be changed.
Therefore, the day we celebrate מתן תורה is the 6th of Sivan and not Yom Kippur when we received the second Luchos. Since we still relate to Har Sinai and our learning is with the experience of Sinai, we also celebrate the giving of the Torah at Sinai.
Rashi says on the pasuk ויהי ערב ויהי בוקר יום הששי:
THE SIXTH DAY — The whole Creation stood in a state of suspense until the sixth day — that is, the sixth day of Sivan which was destined to be the day when the Torah would be given to Israel.
All of creation was in suspense because the giving of the Torah was the completion of the world. The revelation of the Torah is the final revelation of all reality.
["זה השער"]
