Teshuvah and the second Luchos purify Israel

הסעודה שעושין בעיו"כ משום שלא הי' יו"ט לישראל כיוהכ"פ שבו ניתנו לוחות האחרונות.

The festive meal that is held on Erev Yom Kippur is because there was no Yom Tov for Israel like Yom Kippur, on which the second Luchos (Tablets) were given.

The Sefas Emes explains the custom of feasting before Yom Kippur: this day is supremely joyous, for on it Israel received the second set of Tablets.

ולפי שמתענין ביוה"כ מקדימין הסעודה.

And since one fasts on Yom Kippur itself, the meal is moved earlier, to the eve.

Because the day itself is a fast, the celebratory meal of this Yom Tov is shifted to the day before.

ונראה דעיקר שזכו ללוחות אחרונות מכח התשובה שעשו בערב יוכ"פ כי בלוחות הראשונות החטיאם השטן כדי שלא יזכו אל הלוחות ביום האחרון שהי' מוכן משה רע"ה לירד מן ההר למחרת.

And it appears that the main reason they merited the second Luchos was the power of the teshuvah they did on Erev Yom Kippur; for with the first Luchos the Satan caused them to sin, in order that they should not merit the Tablets on the final day, when Moshe Rabbeinu was ready to descend from the mountain the next day.

Israel earned the second Tablets through their teshuvah; with the first Tablets the Satan had engineered the sin of the Golden Calf precisely to rob them of the Luchos just as Moshe was about to bring them down.

ובודאי גם באחרונות עמד השטן בכל כחו לעכב אותן ולהחטיאם.

And surely with the second Luchos too the Satan stood with all his strength to hold them back and cause them to sin.

The same opposition arose the second time — the Satan exerted his full force to prevent Israel from receiving the Tablets again.

ואבותינו גברו עליו ועיקר בעל תשובה באותו מקום באותו הזמן ולפי שעמדו על נפשם זכו לתשובה שלימה וזכו לקבל לוחות אחרונות.

But our forefathers prevailed over him — and the essence of a baal teshuvah is "in that very place, at that very time"; and because they stood firm for their souls, they merited complete teshuvah and merited to receive the second Luchos.

This time Israel overcame the Satan, fulfilling the standard of the true baal teshuvah who withstands the same test in the same place; their firmness won them perfect teshuvah and the second Tablets.

ולכן איתא שהשטן מתגבר בעיו"כ לפי שהיטב חרה לו אשר נצחו אותו ביום הזה.

Therefore it is brought that the Satan grows stronger on Erev Yom Kippur, because it greatly angers him that they defeated him on this day.

The Satan's intensified efforts before Yom Kippur stem from his bitter resentment at having been overcome by Israel's teshuvah on this very day.

ועיקר הכפרה וטהרה ביוכ"פ מכח הלוחות כמ"ש וזרקתי עליכם מים טהורים אין מים אלא תורה.

And the essence of the atonement and purification on Yom Kippur comes from the power of the Luchos, as it says, "and I will sprinkle upon you pure waters" (Yechezkel 36:25) — and "water" refers to nothing other than Torah.

The cleansing of Yom Kippur flows from the Tablets, for the purifying "waters" the navi promises are the waters of Torah.

וצריכין להיות כלי לקבל התורה וזהו מקוה ישראל מה מקוה מטהר כך הקב"ה מטהר את ישראל.

And one must be a vessel (kli) to receive the Torah; and this is "the mikveh of Israel" (mikveh Yisrael, Yirmiyah 17:13) — just as a mikveh purifies, so too HaKadosh Baruch Hu purifies Israel.

To absorb the Torah's waters one must become a fitting vessel; the Mishnah's image of Hashem as Israel's "mikveh" teaches that He purifies them just as a mikveh does.

פירוש שבני ישראל הם מקוה טהרה שמוכנים לקבל מי התורה.

The explanation: that Bnei Yisrael are a mikveh of purity, prepared to receive the waters of Torah.

Israel itself becomes the gathering-basin that is ready to hold the purifying waters of Torah.

וע"ז נרמז יקוו המים כו' אל מקום אחד בנ"י שהם גוי אחד בארץ.

And concerning this it is hinted, "let the waters be gathered… to one place" (Bereishis 1:9) — Bnei Yisrael, who are "one nation in the land" (goy echad ba'aretz).

The verse about waters gathering "to one place" alludes to Israel uniting as one nation, the single basin able to receive the Torah's waters.

ולכן צריכין להיות אגודה אחת ביוכ"פ לזכות לטהרה:

Therefore they must be a single bound bundle (agudah achas) on Yom Kippur in order to merit purification.

Just as a mikveh requires a unified gathering of water, Israel must unite as one on Yom Kippur to become the vessel worthy of purity.

Summary: The Erev Yom Kippur meal celebrates that Yom Kippur is the day Israel received the second Luchos. They merited those Tablets through the teshuvah by which they overcame the Satan "in the same place and time" of their earlier failure — the model of a true baal teshuvah — which is why the Satan rages on this day. The purification of Yom Kippur flows from the Torah, the "pure waters," and to receive them Israel must become a fitting vessel, a "mikveh of purity," by uniting as a single agudah.