Shabbos as the root of Torah

הכל מודים בשבת ניתנה תורה דכתיב זכור בעצומו של יום כו'.

All agree that the Torah was given on Shabbos, as it is written "Remember" — on that very day, etc.

Chazal (Shabbos 86b) state that everyone concedes the Torah was given on Shabbos, derived from the link between "Zachor" (Remember the Shabbos) and the day of the giving of the Torah.

פי' דעיקר קבלת התורה הוא שנתקרבו נפשות בנ"י למקומם ושורשם כמ"ש פנים בפנים דיבר ה' עמכם וכ"כ אנכי ה' אלקיך שראו והשיגו כל אחד כח אלקות שנתן הבורא ית' בכל נפש שבישראל.

The explanation: the essence of receiving the Torah is that the souls of Bnei Yisrael were drawn close to their place and their root, as it says "Face to face Hashem spoke with you," and likewise "I am Hashem your God" — that each one saw and grasped the power of Godliness that the Creator placed in every Jewish soul.

Kabbalas haTorah was not merely receiving a book; it was each Jew's soul reconnecting to its source in Hashem, recognizing the spark of the Divine planted within himself.

והוא באמת בחי' השבת קודש שהוא המנוחה והשביתה שכל דבר חוזר למקומו ושורשו זאת נקרא שבת.

And this is truly the aspect of the holy Shabbos, which is the rest and cessation in which everything returns to its place and its root — this is what is called Shabbos.

Shabbos is precisely this movement of return: every created thing settling back into its source. That is why the Torah, which reunites souls with their root, was given on Shabbos.

וכתיב זכור כו' יום השבת ולא שייך זכירה רק בדבר שכבר השיגו פעם אחת.

And it is written "Remember… the day of Shabbos," and remembering applies only to something that one already attained once.

The command to "remember" implies a prior experience; you can only recall what you once grasped, which points to a moment when the Shabbos-consciousness was already revealed.

ולכן כיון שבעת קבלת התורה הי' בהתגלות בחי' השבת צוה אותם לזכור זאת תמיד.

Therefore, since at the time of receiving the Torah the aspect of Shabbos was revealed, He commanded them to remember this always.

That original revelation of the Shabbos-experience at Sinai is what we are commanded to keep recalling — "Zachor" calls us back to that moment of return to our root.

ובאמת עיקר השבת ניתן מקודם במרה.

And in truth the essence of Shabbos was given earlier, at Marah.

The mitzvah of Shabbos had already been given to Bnei Yisrael at Marah, before Sinai (see Sanhedrin 56b).

אבל עתה השיגו בנפשותם קבלת קדושת שבת.

But now, at Sinai, they attained within their souls the reception of the kedushah of Shabbos.

At Marah it was given as a command, but at Matan Torah they internalized the holiness of Shabbos in their very souls.

והוא באמת ענין נשמה יתירה שניתוסף לכל איש ישראל בש"ק.

And this is truly the matter of the neshamah yeseirah (additional soul) that is added to every Jew on the holy Shabbos.

This soul-attainment of Shabbos kedushah is the source of the extra soul each Jew receives weekly on Shabbos.

והוא על ידי דמתאחדין ברזא דאחד בשבת דכתיב מורשה קהלת יעקב:

And it comes about by means of becoming unified in the secret of the One on Shabbos, as it is written "an inheritance for the congregation of Yaakov."

On Shabbos Bnei Yisrael unite with the "secret of the One" — the absolute oneness of Hashem — and through this the Torah becomes the eternal inheritance of Klal Yisrael.

Summary: The Torah was given on Shabbos because both share one essence — the return of every soul to its root in Hashem. Kabbalas haTorah was each Jew internalizing the kedushah of Shabbos, the source of the neshamah yeseirah, by uniting with the secret of Hashem's oneness.