As Rabbis Riskin and Sachs have pointed out, the shoresh (root word) for a garment, beged, is the same as the shoresh for deception, bagad. And the Torah bears this out – the text has almost no descriptions of clothing at all for Avraham and Isaac and Moshe; the only times clothing is mentioned for Yaakov is when he is pretending to be Esau. Like the fig leaves for Adam and Chava or Tamar’s coverup, clothing in Judaism is seen as deceptive, as masking reality. What really matters is the man, not what he wears.
Megillas Esther is full of deception. From the temple-like adornments of Ahaverush to Esther’s bathing for 6 months in deceptive perfumes, it is all about how clothes hide the inner reality. Without exception, every mention of appearance or dress hides some subterfuge in which the intentions of the wearer does not match his garments.
The obvious exception would seem to be the garments of the Cohanim. The Torah tells us what the priests should wear, in great detail. But if a garment is deceptive, how can this be?
The answer is that garments are deceptive, and those of the cohanim are no exception. But while the garments of Yaakov were used to deceive Isaac, and the royal garments of Esther were to deceive Ahashverush, the garments of the cohanim were not there for G-d, or to fool the Jewish people. The garments of the cohanim were there to deceive themselves.
The role of a cohen is to serve Hashem in his home on earth – the Mishkan and Beis Hamikdash. In this role, every cohen must entirely subsume his individuality behind the requirements of his office; he must not deviate one iota from the prescribed role; this is the human tzimtzum that Rabbi Sachs identifies that was necessary in order to allow coexistence with Hashem’s shechinah.
The garments are there to deceive the neshamah of the cohen wearing them; to convince the neshama that its individual and unique flair is restricted and limited by the garments themselves. Every Cohen Godol must be the same as every other Cohen Godol. The garments deceive.
Note for Purim added by Zev Hall: If Ahaverush wore the garments of the Cohen Godol at his feast, then when Mordechai was dressed up “in the king’s clothes” as Haman led him, then Mordechai was actually wearing the garments of the cohen godol. Since we know that Mordechai was a Benjaminite, the deception thickens! (Zev Hall)