Shabbos HaGadol gathers the year's lights

שמעתי מפה קדוש מו"ז ז"ל על שבת הגדול שמתאספין בו כל הארות שבתות השנה כו'.

I heard from the holy mouth of my grandfather, of blessed memory, regarding Shabbos HaGadol, that all the illuminations of the Shabbosos of the year are gathered into it.

The Sefas Emes transmits a teaching from his grandfather that Shabbos HaGadol is a kind of collecting point into which the spiritual lights of all the year's Shabbosos converge.

והנה הן המה הנ' שערי בינה אשר צריך להיות נפתח שער אחד בכל שבת.

Now, these are the fifty gates of binah (understanding), of which one gate must be opened on each Shabbos.

The illuminations of the year's Shabbosos correspond to the fifty sha'arei binah, with one gate of understanding opening on each Shabbos.

וע"י שריפת פנים טמא בימי המעשה זוכה אח"כ בשבת קודש להארת פנים טהור המכוון כנגדו.

And through the "burning away" of an impure face during the weekdays, one afterward merits, on the holy Shabbos, the illumination of the pure face that corresponds to it.

By burning out the "impure face" (the unrefined aspect) during the labor of the weekdays, a person becomes worthy on Shabbos of the corresponding "pure face" — the matching gate of holy illumination.

והנה ב' השבתות שבת הגדול הוא משער הנ' עלמא דחירות ויש שבת הראשון אשר נקרא ראשית חכמה יראת ה' ובמ"א הארכנו בזה:

Now, of the two Shabbosos: Shabbos HaGadol is from the fiftieth gate, the "world of freedom," and there is the first Shabbos, which is called "the beginning of wisdom is the fear of Hashem" — and elsewhere we have elaborated on this.

He distinguishes two special Shabbosos: Shabbos HaGadol, drawn from the highest fiftieth gate which is the "world of freedom" (alma de-cheirus), and a "first Shabbos" associated with yiras Hashem, "the beginning of wisdom" — the entry point of avodah.

Summary: Shabbos HaGadol gathers into itself all the illuminations of the year's Shabbosos, which correspond to the fifty gates of binah, one opening each Shabbos. By burning away the "impure face" through weekday labor, one merits the matching "pure face" of illumination on Shabbos. Shabbos HaGadol itself draws from the loftiest fiftieth gate, the world of freedom, in contrast to the "first Shabbos" of yiras Hashem, the beginning of wisdom.