Kohen's holiness drawn from the people

בפסוק וקדשתו כו'.

On the verse "And you shall sanctify him" (Vayikra 21:8), etc.

The Torah commands that Bnei Yisrael are to sanctify the kohen; the Sefas Emes asks what this sanctifying really means.

פי' שקדושת הכהנים תלוי בקדושת בנ"י שצריכין להתקדש אף מי שא"י להיות קדוש ממש אעפ"כ מעט קדושה שלו מוסיף כח לזה האיש המיוחד לקדושה להתקדש כראוי.

The meaning is that the holiness of the kohanim depends on the holiness of Bnei Yisrael, who must sanctify themselves. Even one who cannot become truly holy — nonetheless his small measure of kedushah adds strength to this man set apart for holiness, enabling him to be sanctified as is fitting.

The kohen's kedushah is not his alone; it is fed by the collective sanctity of every Jew. Even a person who reaches only a little kedushah contributes that portion, empowering the kohen — who is designated for holiness on behalf of all — to be fully sanctified.

וכ"כ הכהן הגדול מאחיו.

And so too: "the kohen who is greater than his brethren" (Vayikra 21:10).

The Torah's description of the Kohen Gadol as "greater than his brethren" hints at the source of his greatness.

דרשו חז"ל גדלהו משל אחיו והוא כדברינו הנ"ל והבן:

Chazal expounded: "Make him great from that of his brethren" — and this accords with our words above, and understand.

The Kohen Gadol is made great "from that of his brethren" — his elevated kedushah is literally built up from the contributions of all his fellow Jews, exactly the principle stated above.

Summary: The holiness of the kohanim, and of the Kohen Gadol "greater than his brethren," is not self-generated but drawn from the collective kedushah of all Bnei Yisrael — even the small measure of one who cannot become fully holy adds strength to the one designated to be sanctified on everyone's behalf.