Based on this, I once heard a very beautiful idea. Immediately after Yom Kippur, the very first Pasuk we recite in Maariv is:
וְהוּא רַחוּם יְכַפֵּר עָוֹן וְלֹא יַשְׁחִית וְהִרְבָּה לְהָשִׁיב אַפּוֹ – And He, being merciful, forgives iniquity and does not destroy, and frequently turns away His anger. But what עָוֹן? What sin and iniquity? Wasn’t Yom Kippur just concluded a moment earlier? Didn’t Hakadosh Baruch Hu just wash us clean, atone for us, and purify us from all our sins? You already hear a heavenly voice – and what does the bat kol declare?
כִּי כְבָר רָצָה הָאֱלֹהִים אֶת־מַעֲשֶׂיךָ לֵךְ אֱכֹל בְּשִׂמְחָה לַחְמֶךָ וּשְׁתֵה בְלֶב־טוֹב יֵינֶךָ
Go, eat your bread in gladness, and drink your wine in joy; for your action was long ago approved by G-d.
Why, then, the need to speak immediately of atonement once again? Rabbotai, I heard from Rav Alkrief that the answer is found in the yesod: תְּפִלָּה עוֹשֶׂה מֶחֱצָה – Tefillah accomplishes half. One davens, and their Tefillah accomplishes half the job. Where do we learn this? Kayin was decreed to be both a wanderer and a fugitive – נָע וָנָד. He davened, and Hakadosh Baruch Hu canceled half the decree – he remained only a fugitive (נָד), residing in אֶרֶץ נֹוד. Aharon HaKohen, after the Cheit HaEigel, was decreed to lose all his sons. He davened, and only half the decree was carried out. Nadav and Avihu died, but Elazar and Itamar remained. Tefillah accomplishes half.
So too on Yom Kippur. We recite viduy and confess ten times. Ten confessions, corresponding to the five immersions (טְבִילוֹת) and ten sanctifications (קִדּוּשִׁים) of the Kohen Gadol. Each confession erases half of what remains. Imagine – even if a person had violated all 613 Mitzvot, the first viduy cuts that number in half, the second halves it again, the third halves it again, and so on. By the tenth confession, almost nothing remains – just a sliver, a small fraction. That is why after Yom Kippur we say וְהוּא רַחוּם יְכַפֵּר עָוֹן – for the tiny fraction of iniquity left behind, Hakadosh Baruch Hu forgives in His mercy.
Thus, the first lesson after Yom Kippur is this: the day itself has lifted us to a level of purity, but it is Torah and Tefillah together that seal it.
When we emerge from Yom Kippur, purified, the question is: what do we do with that new state? In the Haftarah of Shabbat Shuva we read:
שׁוּבָה יִשְׂרָאֵל עַד ה' אֱלֹהֶיךָ כִּי כָשַׁלְתָּ בַּעֲוֺנֶךָ קְחוּ עִמָּכֶם דְּבָרִים וְשׁוּבוּ אֶל־ה'
Return, O Israel, to Hashem your G-d, for you have stumbled in your iniquity. Take words with you and return to Hashem.
Chazal ask, what are these דְּבָרִים – words, we’re supposed to take with us? The Midrash explains, Devarim means Divrei Torah. Teshuva without Torah is incomplete; real Teshuva means: הֲשִׁיבֵנוּ אָבִינוּ לְתוֹרָתֶךָ. Rav Chaim Volozhin explains that is why the Anshei Knesset HaGedolah placed those exact words in the Bracha of Teshuva, as Torah is the doorway to Teshuva.
The Zohar adds: distancing from Torah is distancing from Hakadosh Baruch Hu, and closeness to Torah is closeness to Him. If a person wants to hold onto the closeness of Yom Kippur, there is only one path: Torah.
This also helps explains the piyyut we sing in Musaf, at least amongst Bnei Ashkenaz:
אֱמֶת מַה נֶּהְדָּר הָיָה כֹּהֵן גָּדוֹל בְּצֵאתוֹ מִבֵּית קָדְשֵׁי הַקֳּדָשִׁים בְּשָׁלוֹם בְּלִי פֶגַע
How truly glorious was the High Priest as he left the Holy of Holies, peacefully, unharmed.
Notice, it does not speak of how he entered the Kodesh Kodashim, but rather, how he emerged from it. Seeing how glorious his entry was is no chochma – as there were some who entered in such a manner but never made it out; they died in the Kodesh HaKodashim! The greatness of Yom Kippur is not how we entered, but how we emerge. Do we emerge and go directly into Mitzvot? Do we run to build a sukkah? Do we return to Torah? That is the true measure of the day!
Chazal say, אֱמֶת מַה נֶּהְדָּר הָיָה כֹּהֵן גָּדוֹל, and in truth, each one of us is like the Kohen Gadol who enters to serve on Yom Kippur. Today we no longer have a Kohen Gadol in the Beit HaMikdash, but every Jew, through his Avodah on Yom Kippur, is as if he has stepped into the Holy of Holies. So we say: “How splendid was the Kohen Gadol when he emerged from the Holy of Holies,” and the question is – what do you do when you emerge? What do you do when you step out of Yom Kippur? The answer is clear. You come to a shiur, you sit down immediately – a Daf Yomi shiur, a Parsha shiur, this is how you emerge! This is the glory of the Kohen Gadol emerging from the Yom Kippur Avodah. The central thing we want to show Hakadosh Baruch Hu is that the very moment we emerge from Yom Kippur, the first thing we do is immerse ourselves again in Torah. Why? Because this is the true power of Teshuva: הֲשִׁיבֵנוּ אָבִינוּ לְתוֹרָתֶךָ וְקָרְבֵנוּ מַלְכֵּנוּ לַעֲבוֹדָתֶךָ.
The Reishit Chochma writes that the highest form of Teshuva is Torah studied with awe and with love. The Chatam Sofer, in his drasha for Shabbat Shuva also teaches that Torah is the greatest tool for repentance. R’ Yitzchak Isaac Chaver in his sefer Ohr HaTorah says the same, and the Gemara makes it clear: בָּרָאתִי יֵצֶר הָרָע בָּרָאתִי לוֹ תּוֹרָה תַּבְלִין – I created the evil inclination, I created the Torah as its antidote (Kedushin 30b).
This is the answer even to Kayin. Hakadosh Baruch Hu told him: הֲלוֹא אִם תֵּיטִיב שְׂאֵת – Is this not so, if you improve, there is forgiveness, and Chazal say: אֵין טוֹב אֶלָּא תּוֹרָה – There is no good except Torah. If you take hold of the Torah, and allow it to be a lamp for your feet, it will guide you, it will lift you up, and through it your sins will be atoned. But if you do not do good – if you do not engage in Torah – then, as the Pasuk continues, לַפֶּתַח חַטָּאת רֹבֵץ – sin crouches at the door. Without Torah, you will inevitably fall back into the same sins. The only true path out, the only way to rise above, is through the holy Torah.
