Torah as the bond to supernal festivals

והיית אך שמח לרבות לילי יו"ט האחרון כו' הוא כנ"ל שע"י ששומרין ימי החג כראוי.

"And you shall be only joyful" (Devarim 16:15) — comes to include the night of the last Yom Tov, etc. — this is as explained above, that through keeping the days of the Festival properly,

Chazal expound "ach sameach" to add the night of the final Yom Tov (Shemini Atzeres). The Sefas Emes connects this to the earlier idea: proper observance of the seven days of the chag is what enables this added joy.

הוא הבטחה שיהי' להם שייכות לשמוח גם בשמיני שהוא למעלה מהטבע כנ"ל.

it is a guarantee that they will have a connection to rejoice also on the eighth day, which is above nature, as above.

Keeping the seven days assures Bnei Yisrael a portion in the joy of Shemini Atzeres, the day that transcends the natural order.

[ועמ"ש למעלה אך למעט האומות גם א"ך גי' אהי' ושם שלח תשלח כו' רק הבנים תקח].

[And see what is written above, that "ach" comes to exclude the nations; also "ach" (אך) is the gematria of "Ehyeh" (אהי-ה = 21); and there, "you shall surely send away" (Devarim 22:7), etc. — only "the children you shall take."]

The Sefas Emes adds two hints in a bracket: the word "ach," while limiting the nations, equals in gematria the Divine Name "Ehyeh"; and the language of "shaleiach teshalach... the children you shall take" echoes the theme that the nations are sent away while the "children" (Bnei Yisrael) are drawn in close.

והנה בכל מועד יש מצוה מיוחדת.

And behold, on every festival there is a special mitzvah.

The Sefas Emes observes that each of the festivals has its own distinctive mitzvah tied to it.

מצה בפסח.

Matzah on Pesach.

Pesach has the mitzvah of eating matzah.

סוכה וד' מינים בסוכות.

Sukkah and the four species on Sukkos.

Sukkos has the mitzvos of dwelling in the sukkah and taking the arba minim.

לבד שבועות ושמ"ע אין מצוה.

Except for Shavuos and Shemini Atzeres, which have no special mitzvah.

Two festivals stand out as having no unique physical mitzvah of their own: Shavuos and Shemini Atzeres.

זולת בביהמ"ק שהי' קרבנות המוספין.

Apart from in the Bais Hamikdash, where there were the Musaf offerings.

The only distinctive mitzvah of these two days was the Musaf korbanos brought in the Bais Hamikdash, not a mitzvah performed everywhere.

והענין שב' מועדות האלו הם מעולם העליון.

And the matter is that these two festivals are from the supernal world.

The reason they lack a physical mitzvah is that Shavuos and Shemini Atzeres derive from the upper, supernal world.

ואין להם התדבקות במצות מעשיות.

And they have no attachment to practical, physical mitzvos.

Because they belong to a realm above nature, they cannot be grasped through ordinary action-based mitzvos rooted in the physical world.

לכן העצה ע"י התורה.

Therefore the counsel is by means of the Torah.

The way to connect to these supernal days is not through physical mitzvos but through Torah itself, which bridges the upper world and ours.

בשבועות מתן תורתינו ובשמ"ע שמחת תורה שבע"פ.

On Shavuos, the giving of our Torah (mattan Torah); and on Shemini Atzeres, the joy of the Oral Torah (Torah she-be'al peh).

Each of these two festivals is bound to Torah: Shavuos to the receiving of the Written Torah, and Shemini Atzeres to the celebration of the Oral Torah on Simchas Torah.

שע"י התורה יכולין להתדבק גם במה שלמעלה מהטבע.

For through the Torah one is able to cleave even to that which is above nature.

The Torah uniquely empowers a person to attach himself to the supernatural realm that physical mitzvos cannot reach.

ז"ש תמימה משיבת נפש שאין לנו בעוה"ז בגלות במה להתדבק ביו"ט הללו.

This is the meaning of "[the Torah of Hashem is] perfect (temimah), restoring the soul" (Tehillim 19:8) — for we have nothing in this world, in galus, by which to attach ourselves on these festivals,

The Torah is called "temimah" because it is whole and complete. The Sefas Emes applies this to our situation: in galus, deprived of the Bais Hamikdash and its korbanos, we have no other means to bond with the lofty days of Shavuos and Shemini Atzeres.

רק ע"י התורה הזאת:

except through this Torah.

Torah alone remains our means of clinging to Hashem on these supernal festivals — it restores the soul and connects us to what lies above nature even amid the darkness of galus.

Summary: The added joy of "ach sameach" on Shemini Atzeres is earned through proper observance of the seven days of the chag. Every festival has its own special mitzvah, but Shavuos and Shemini Atzeres — which derive from the supernal world above nature — have none beyond the Musaf korbanos. The means of connecting to these lofty days is therefore the Torah itself: the Written Torah on Shavuos and the Oral Torah on Simchas Torah. Especially in galus, with no Bais Hamikdash, it is only through the perfect, soul-restoring Torah that we can cleave to that which is above nature.