Love for Hashem covers shortcomings

במדרש בני לוי שקירבו עצמם לי כו'.

In the Midrash: "the sons of Levi, who drew themselves close to Me etc."

The Midrash highlights that Levi earned its standing by actively drawing itself near to Hashem.

כבר כ' בשם מו"ז בענין ויאספו אליו בני לוי.

It has already been written in the name of my grandfather regarding "and the sons of Levi gathered to him [Moshe]."

He recalls a teaching of his grandfather on the moment after the eigel when Shevet Levi rallied to Moshe Rabbeinu's call.

כי הגם שהי' בודאי כמה בבנ"י שלא חטאו רק שלא הי' להם הכח ע"י החטא שנעשה בישראל להכניס עצמם בשם מי לה' אלי עכ"ד.

For although there were surely many among Bnei Yisrael who had not sinned, yet because of the sin that had occurred in Yisrael they lacked the strength to place themselves under the banner of "Whoever is for Hashem, to me!"; thus far his words.

Even Yidden innocent of the eigel were so weakened by the collective sin that they could not muster the courage to step forward when Moshe called — this concludes the grandfather's teaching.

ובני לוי שהי' בהם דביקות עצום שע"ז נקראו בני לוי לא נתרשל ידם על ידי החטא.

But the sons of Levi, who possessed an intense deveikus (attachment to Hashem) — for which they are called "bnei Levi" (from the root of joining/clinging) — their hands did not slacken on account of the sin.

Levi's very name expresses clinging to Hashem; their powerful deveikus kept them steady and unshaken even amid the people's failure.

וכענין שכ' על כל פשעים תכסה אהבה זה הוא בהאדם עצמו ג"כ כפי אהבה ותשוקה שבו להשי"ת אינו מתפעל ע"י קצת שפלות שבו והאהבה מכסה החסרונות וזה סימן שהוא בכלל מי לה' כו':

And it is like that which is written, "love covers over all transgressions" — this applies within the person himself as well: according to the love and yearning he has for Hashem, he is not shaken by some lowliness within him, and the love covers over the shortcomings; and this is a sign that he is included among "Whoever is for Hashem."

Just as love covers faults between people, a person's own ahavah for Hashem keeps him from being thrown by his lapses; that resilience is itself the mark of one who truly belongs to the side of Hashem.

Summary: After the cheit ha'eigel, even Yidden who had not sinned felt too weakened to step forward at Moshe's call of "Whoever is for Hashem, to me!" Shevet Levi, whose very name bespeaks deveikus, were not paralyzed because their intense attachment to Hashem held firm. The same works within each person: strong ahavah for Hashem "covers over" one's own shortcomings, so that occasional lowliness does not cause despair — and that very steadfastness is the sign of one who stands "for Hashem."