Torah received ripens into joy

ענין שמחת תורה בשמ"ע.

The matter of Simchas Torah on Shemini Atzeres.

The Sefas Emes opens by asking why the rejoicing over the Torah is set specifically on Shemini Atzeres.

דבשבועות הוא קבלת התורה.

For on Shavuos there is the receiving of the Torah.

Shavuos is the season of kabbalas haTorah, the initial giving and accepting of the Torah.

וגמר הפרי ופעולה שנעשה באדם ע"י קבלת התורה נגמר עתה.

And the ripening of the fruit and the effect produced in a person through the receiving of the Torah is completed now.

What was planted on Shavuos only now comes to full fruition; the inner change wrought by the Torah reaches its completion at this time.

כי כן סדר רגלים של השנה.

For such is the order of the Festivals of the year.

The cycle of the three Regalim follows the rhythm of an agricultural year, from planting to harvest.

פסח ראשית קצירכם.

Pesach is "the beginning of your harvest."

Pesach marks the first cutting, the beginning of the avodah, like the start of the reaping season.

וסוכות חג האסיף גמר כל העבודה.

And Sukkos is the "Festival of Ingathering," the completion of all the avodah.

Sukkos is the season of gathering everything in — the finishing of the entire year's spiritual labor.

ועל זה נאמר טוב אחרית דבר מראשיתו.

And about this it is said, "The end of a matter is better than its beginning."

The completed fruit at the close is greater than the seed at the start; hence the joy of the conclusion.

לכן איתא בזוה"ק פ' תצוה כי כפי תיקון ימי הספירה כך אין לירא בימי הדין בתשרי ע"ש:

Therefore it is brought in the holy Zohar, Parshas Tetzaveh, that according to one's rectification (tikkun) during the days of Sefirah, so one need not fear during the days of judgment in Tishrei — see there.

The work of refinement done between Pesach and Shavuos secures a person so that the Days of Judgment of Tishrei hold no dread, and the season can close in pure simchah.

Summary: Just as the festival year moves from the first harvest of Pesach to the ingathering of Sukkos, so the Torah received on Shavuos ripens within a person and reaches its completed fruit on Shemini Atzeres — and one who refined himself during Sefirah comes to the Tishrei judgment without fear, able to rejoice fully on Simchas Torah.