The restored song of the eighth day

בפסוק וירא כל העם וירונו.

On the verse, "And all the people saw, and they sang out for joy" (Vayikra 9:24).

The Sefas Emes opens from the verse describing the people's reaction when fire descended on the eighth day of the Mishkan's inauguration.

ולא כתיב מה אמרו.

And it does not state what they said.

The verse records that the people sang out, yet conspicuously omits the words of their song — a silence that calls for explanation.

אבל היא השירה ראשונה שפתחו בנ"י בקריעת י"ס שהי' שירה לדורות כמ"ש שם.

But it is the same first shirah (song) that Bnei Yisrael began at Krias Yam Suf, which was a song for all generations, as it is written there.

The unstated song was none other than the Shiras HaYam, the original song of redemption at the splitting of the sea — a shirah meant to resound through all future generations.

וע"י החטא נפסק מהם השירה.

And through the sin (of the golden calf), the song was cut off from them.

The cheit ha'egel interrupted this ongoing song; the flow of shirah that had begun at the sea was severed by the people's fall.

וע"י התיקון עתה חזרו לבחי' השירה כנ"ל.

And through the tikkun (rectification) now, they returned to the aspect of song, as above.

With the inauguration of the Mishkan, the sin was repaired, and Bnei Yisrael could once again reconnect to that interrupted song of joy.

ורמז לזה איתא בזוה"ק דמשעת קי"ס לא הוי חדוה כההוא חדוה דיום השמיני ע"ש:

And a hint to this is found in the Zohar HaKadosh, that from the time of Krias Yam Suf there was no joy like that joy of the eighth day. (See there.)

The Zohar confirms the connection: the simchah of the Mishkan's eighth day matched the joy of the sea precisely because it restored the very same song, completing the circle from the redemption to its rectification after the calf.

Summary: When fire descended on the eighth day of the Mishkan's dedication, the people "sang out" — but the Torah omits the words because it was the very same Shiras HaYam first sung at the sea, a song meant for all generations. That song had been cut off by the sin of the golden calf; the rededication of the Mishkan was its tikkun, restoring Bnei Yisrael to song and to a joy unmatched since the splitting of the sea, as the Zohar attests.