“…And he shall remove the linen garments that he had worn when he came into the Holy, and there he shall leave them…” – Vayikra 16:23

וּפָשַׁט אֶת בִּגְדֵי הַבָּד אֲשֶׁר לָבַשׁ בְּבֹאוֹ אֶל הַקֹּדֶשׁ וְהִנִּיחָם שָׁם – ויקרא טז, כג

On the words “and there he shall leave them,” Rashi comments that the Yom Kippur garments of the Kohen Gadol were single-use only; they were stowed away after the service of Yom Kippur and never used again, even for a future Yom Kippur.

This unique law reflects the essential theme of Yom Kippur: teshuva, repenting and returning to G-d and His service. Teshuva is characterized by reinvention. The penitent redirects the course of his life, reinventing his identity and character. In fact, the Rambam writes that the penitent even changes his name, “as if to say ‘I am a different person and not the same one who sinned’” (Hilchos Teshuva 2:4).

The ultimate Yom Kippur experience was that of the Kohen Gadol, “when he came into the Holy,” upon entering the Kodesh Hakadashim. (And as representative of the entire Jewish nation, the Kohen Gadol’s experience on Yom Kippur is the source from which all Jews draw the strength for their “Yom Kippur makeover”—a total transformation through Teshuva.) It follows that the Kohen Gadol was a changed person after being in the Kodesh Hakadashim on Yom Kippur. He would emerge a new man, even in comparison to his “reinvention” on the Yom Kippur in previous years. Therefore, reflecting his inner transformation, his garments for Yom Kippur must likewise be entirely new, and not just a rerun and reuse of those he wore in the past.

—Likutei Sichos, vol. 28, pp. 224-225