The tzaddik who descends to uplift

במדרש על פסוק לך רד.

In the Midrash on the verse, "Go, descend" (Shemos 32:7).

The Sefas Emes begins from the Midrash on Hashem's command to Moshe Rabbeinu to descend from the mountain after the sin of the Egel.

מלאכי אלקים עולים ויורדים בו כו' ע"ש.

"Angels of God ascending and descending upon it" (Bereishis 28:12) — see there.

He links the command to descend with Yaakov's ladder, where the angels go both up and down — implying that descent itself has a holy purpose.

הענין הוא כי גם הירידה הוא לימוד מדריגה של הצדיקים שע"י שבירידת ישראל מורידין עצמם עמהם עי"ז מעלין אח"כ הכל.

The idea is that even the descent is a [teaching of a] level of the tzaddikim: that when Yisrael fall, [the tzaddikim] lower themselves together with them, and through this they afterward raise everything back up.

A true tzaddik does not stay aloof when the people fall; he descends to their level so that he can later lift them — and all of them — back up.

הרי הוא אומר ואעשה אותך לגוי גדול.

For He says, "And I will make you into a great nation" (Shemos 32:10).

Hashem offered Moshe Rabbeinu the chance to separate from the people and become a great nation on his own.

ומיאן מרע"ה בזה.

But Moshe Rabbeinu refused this.

Moshe would not accept becoming great at the cost of abandoning Bnei Yisrael.

ולכך שיבר הלוחות כמ"ש במ"א שע"י שלא רצה להפריש עצמו מכלל ישראל ומסר חלקו לצבור לכן היו אותיות פורחות כי בכלל הי' החטא ע"ש.

And therefore he broke the Luchos, as explained elsewhere: because he did not wish to separate himself from Klal Yisrael and gave over his own portion to the community, therefore the letters flew off, for the sin was [shared] within the whole.

By shattering the Luchos, Moshe joined his own fate to the people's rather than holding himself apart; the letters flew away because he refused to keep the Torah as his private possession while the nation had sinned.

וזה למד מרע"ה ממאמר לך רד הנ"ל וזכה וזיכה את הרבים והעלה כולם כמ"ש אח"ז לך עלה כו' אתה והעם כו':

And this Moshe Rabbeinu learned from the saying "Go, descend" mentioned above, and he merited and brought merit to the many and raised them all up, as it says afterward, "Go up… you and the people…" (Shemos 33:1).

From the very command to "descend," Moshe grasped the avodah of going down to lift the people; having joined them in their fall, he could then be told "go up… you and the people" — raising the entire nation along with himself.

Summary: The command "Go, descend" teaches the avodah of the tzaddik who lowers himself to share in the fall of Bnei Yisrael. Moshe Rabbeinu refused to be made a separate "great nation," broke the Luchos rather than keep the Torah apart from the sinning people, and precisely because he descended with them he was able to raise them all back up.