Purification Yielding Inner Joy
שירת האזינו כולל כל הדורות מבריאות עולם ויציאת מצרים וקבלת התורה וביהמ"ק וגלות וגאולה אחרונה
The Shiras Ha'azinu encompasses all the generations, from the creation of the world, the exodus from Mitzrayim, the receiving of the Torah, the Beis HaMikdash, galus, and the final geulah.
The song of Ha'azinu spans the entire sweep of Jewish history, from creation through the final redemption.
ומעין זה נתחדש בכל שנה כל הסדר כי כך מדותיו של הקב"ה תמים פעלו ואפילו בכל יום יש בו מעין כל הבריאה
And something of this nature is renewed every single year, the entire order of events, for such are the ways of the Holy One, Blessed is He, 'His work is perfect' (Devarim 32:4) — and even within each day there is a taste of the whole of creation.
Because Hashem's conduct is perfect and complete, that same full cycle is renewed each year, and a hint of all of creation is even contained in every single day.
וכן במועדות חג המצות יציאת מצרים ואח"כ קבלת התורה
And so too it is with the Yamim Tovim: Chag HaMatzos corresponds to the exodus from Mitzrayim, and afterward the receiving of the Torah.
The festivals mirror this same sequence: Pesach recalls the exodus, and Shavuos the giving of the Torah.
וסוף הפרשה ראו עתה כו' אני אמית ואחי' הוא בחי' ר"ה ויוהכ"פ ספרי חיים ומתים פתוחין
And the end of the parsha, 'See now... I bring death and I bring life' (Devarim 32:39), is the aspect of Rosh Hashanah and Yom Kippur, when the books of the living and of the dead lie open.
The verse 'I bring death and I bring life' corresponds to the Days of Awe, when the books recording who shall live and who shall die are open before Hashem.
ואח"כ הרנינו גוים עמו הוא בחג הסוכות שרומז לגאולה האחרונה
And afterward, 'Sing out, O nations, His people' (Devarim 32:43) — this is on Chag HaSukkos, which alludes to the final geulah.
The following verse, calling on the nations to sing, points to Sukkos and to the ultimate redemption.
ובאמת אמית ואחי' בימי המשפט הכל לצורך תיקון העולם
And in truth, 'I bring death and I bring life' during the days of judgment is all for the sake of the tikkun of the world.
The death and renewal of the judgment days are not destruction for its own sake but serve to repair and perfect the world.
כדאיתא אני אמית וכי הקב"ה ממית
As it is brought down regarding 'I bring death' — does the Holy One, Blessed is He, then bring death?
The midrash asks pointedly: does Hashem actually deal out death?
אך שממית הפסולת וסט"א ומחיה לכח הפנימיות
Rather, that He puts to death the waste and the sitra achra, and gives life to the inner power.
The resolution is that He puts to death only the waste and the forces of impurity, while enlivening the inner, holy core.
ולכן ממית ומחיה ומצמיח ישועה ומן המיתה בא ג"כ הישועה
And therefore He brings death and brings life and causes salvation to sprout — and from the death itself the salvation also comes.
Thus death and life and salvation all flow together, and the very act of putting the dross to death is itself the source of the salvation.
וכן הוא בכלל שמתבררין נפשות בנ"י בימים האלו כמ"ש יכפר עליכם לטהר אתכם
And so it is in a general sense, that the souls of Bnei Yisrael are clarified and refined in these days, as it is written, 'He shall atone for you to purify you' (Vayikra 16:30).
On a broad level, the souls of Bnei Yisrael are purified and refined during these days, as the verse about Yom Kippur's atonement and purification teaches.
ולכן אחר יוהכ"פ צריכין לקבל עבודת השי"ת בשמחה
And therefore, after Yom Kippur, one must take upon himself the avodah of Hashem with simchah.
Once Yom Kippur has cleansed us, the proper response is to embrace serving Hashem with joy.
כדאיתא בדור המדבר אחר שמחל להם הקב"ה החטא והקימו המשכן ויעמדו לפני ה' קרבו בשמחה ובזריזות לעבודת הבורא
As it is brought down regarding the generation of the wilderness: after the Holy One, Blessed is He, forgave them the sin and they erected the Mishkan and 'stood before Hashem,' they drew near to the avodah of the Creator with simchah and with zerizus.
The midrash illustrates this with the desert generation: after being forgiven for the sin and building the Mishkan, they approached Hashem's service with joy and eagerness.
וכן הוא בחג הסוכות
And so it is on Chag HaSukkos.
This same pattern of post-atonement joy is expressed on Sukkos.
ובזמן המקדש כשהלבין החוט בודאי נתמלאו בנ"י בשמחה
And in the time of the Mikdash, when the crimson thread turned white, surely Bnei Yisrael were filled with simchah.
In Temple times, the crimson thread turning white was a visible sign of forgiveness that surely filled Bnei Yisrael with joy.
וגם עתה צריכין להאמין כי נטהרנו מעונותינו
And even now one must believe that we have been purified from our sins.
Even without that open sign today, we are obligated to believe that Yom Kippur has truly purified us from sin.
ובאמת זה האות כפי מה שמרגיש האדם שמחה בנפשו
And in truth, this is the sign — according to how much a person feels simchah within his neshamah.
The real indicator of that purification is the measure of joy a person senses in his own neshamah.
וגם זה תליא כפי המרירות וצער שיש להאדם מהחטאים כך מרגיש אחר יוהכ"פ השמחה
And this too depends on the bitterness and pain that a person has over his sins; in that measure does he feel the simchah after Yom Kippur.
The depth of one's post-Yom Kippur joy is proportional to the genuine pain and bitterness he felt over his sins.
וזהו שמחת החג אחר יו"כ וניתן לבנ"י
And this is the simchah of the Yom Tov after Yom Kippur, which was given to Bnei Yisrael.
This explains the joy of the Yom Tov that follows Yom Kippur, a gift granted to Bnei Yisrael.
כמ"ש במ"א פי' לב יודע מרת נפשו ובשמחתו לא יתערב זר:
As I have explained elsewhere the meaning of 'The heart knows the bitterness of its soul, and in its joy no stranger shall share' (Mishlei 14:10).
As explained elsewhere, the verse from Mishlei teaches that this joy, born of inner bitterness over sin, is intensely personal and cannot be shared by any outsider.
Summary: The Sfas Emes teaches that Shiras Ha'azinu contains the entire arc of history, from creation to the final geulah, and that because Hashem's ways are perfect, this whole cycle is renewed each year through the festivals and even each day. The verse 'I bring death and I bring life' corresponds to the Days of Judgment, when Hashem puts to death the waste and the sitra achra while enlivening the inner holy core — so that the very 'death' becomes the source of salvation and the tikkun of the world. Through this process the neshamos of Bnei Yisrael are clarified and purified, as on Yom Kippur, and the proper response to such purification is to serve Hashem with simchah, as the desert generation did after the Mishkan was built. Even today, without the visible sign of the crimson thread turning white, we must believe we have been cleansed, and the measure of joy a person feels within his neshamah is itself the sign of that purification. This inner simchah, born in proportion to the bitterness one felt over his sins, is the joy of the Yom Tov following Yom Kippur — a deeply personal joy that, as Mishlei teaches, no stranger can share.