Removing dross unites the souls of Bnei Yisrael

במדרש וישלחו מן המחנה כו'.

In the Midrash: "And they shall send out from the camp etc." (Bamidbar 5:2)

The Sefas Emes opens with the command to send the impure out of the camp, which the Midrash links to the purification of metal.

הגו סיגים מכסף כו'.

"Remove the dross from the silver etc." (Mishlei 25:4)

The Midrash's prooftext compares the sending out of the impure to refining silver by removing its dross — separating the worthless from the precious.

בא להראות איך יכולין בעוה"ז להפשיט עצמו מהטומאה ולברר כל המעשים ע"י שיש בכח נפשות בנ"י זה הבירור שכבר נזדככו פעם אחת בעמדם בהר סיני דכתיב פנים בפנים דיבר.

It comes to show how, in this world, one can strip himself of impurity and clarify all his deeds — because there is within the souls of Bnei Yisrael the power for this refinement, since they were already purified once when they stood at Har Sinai, as it is written: "Face to face He spoke." (Devarim 5:4)

A Jew can cleanse himself of tumah and refine all his actions because the capacity for this purification is already embedded in his soul. At Har Sinai, when Hashem spoke "face to face," Bnei Yisrael were thoroughly purified — and that purification left a permanent power within them.

נפשי יצאה בדברו.

"My soul departed when He spoke." (Shir HaShirim 5:6)

At the giving of the Torah the very souls of Bnei Yisrael left them from the intensity of Hashem's word — an experience of total bittul that scoured away every impurity.

ואז נבדל מהם כל מיני פסולת כדכתיב כהמס דונג מפני אש כו'.

And then every kind of dross was separated from them, as it is written: "as wax melts before fire etc." (Tehillim 68:3)

At Sinai every trace of "dross" — spiritual impurity — melted away from them, like wax dissolving before fire.

וממילא אף שאחר החטא חזרו למומם עכ"ז שוב לעולם בנקל לחזור ולתקן עצמם.

And consequently, even though after the sin they returned to their blemish, nevertheless it is forever easy for them to return and repair themselves.

Although the sin of the Golden Calf reintroduced blemish, the original Sinai purification left an enduring imprint — so it remains forever within reach for Bnei Yisrael to do teshuvah and refine themselves again.

וכל מעשיהם בכח התורה כי באמת כשנבדל הפסולת מתחברין נפשות בנ"י ונעשין אחד.

And all their deeds are by the power of the Torah; for in truth, when the dross is separated, the souls of Bnei Yisrael join together and become one.

The power behind all their refinement is the Torah. When the impurity is removed, what remains is the pure core of the souls — and these pure souls naturally unite, becoming one.

וז"ש ויצא לצורף כלי כי הפסולת מבדיל ועושה פירוד בין בנ"י.

And this is the meaning of "and a vessel emerges for the refiner" (Mishlei 25:4) — for the dross divides and creates separation among Bnei Yisrael.

Once the dross is removed, a finished "vessel" emerges. The lesson: impurity is precisely what causes division and fragmentation among Bnei Yisrael, while its removal allows them to unite.

ובכל עת שמתגלה הארת התורה והקדושה מתברר הפסולת.

And at every time that the light of the Torah and kedushah is revealed, the dross is clarified away.

Whenever the illumination of Torah and holiness shines forth, it acts like a refining fire, separating out and removing the impurity.

וכמו כן בש"ק ויברך ויקדש ממילא מתעברין מיני' כל סט"א.

And likewise on Shabbos Kodesh — "and He blessed and sanctified" (Bereishis 2:3) — automatically all the sitra achra is removed from it.

Shabbos works the same way: because Hashem blessed and sanctified it, the kedushah of Shabbos automatically expels all the sitra achra, the forces of impurity.

ואין צריך בירור שוב ועי"ז מתאחדין בי' בנ"י ברזא דאחד:

And there is no need for further refinement, and through this Bnei Yisrael are unified on it in the secret of oneness (raza de'echad).

On Shabbos no additional effort of refinement is required — the dross is gone of itself. As a result, the pure souls of Bnei Yisrael are bound together on Shabbos in the deep "secret of oneness," achieving complete achdus.

Summary: Refining oneself from tumah is like removing dross from silver, and Bnei Yisrael have the inner power for it because they were purified at Har Sinai — an imprint that makes teshuvah forever attainable despite later sin. Impurity is what causes division among Jews, so whenever the light of Torah and kedushah shines it removes the dross and lets the pure souls unite. On Shabbos this happens automatically: its holiness expels all impurity and binds Bnei Yisrael together in the secret of oneness.