The story of Megillas Esther is punctuated by references to clothing. At his lavish royal parties, Achashveirosh wears the special garments of the Kohen Gadol (Esther 1:4 and Megillah 12a). When Mordechai hears of Haman's decree, he rips his clothing and puts on sackcloth (Esther 4:1). Before Esther enters the king's chamber, she dresses in royal garments (5:1). Haman expresses his desire to be dressed in royal clothing (6:8). And finally, after Haman's plan is foiled, Mordechai leaves the king's presence wearing royal clothing (8:15). What is the message behind these multiple references to clothing? What's more, the custom on Purim is to dress up in costumes and masks. What is the idea behind this type of masquerade?
In Parshas Tetzaveh, the Torah instructs Moshe to make special clothing for the kohanim - l'chavod u'l'sifares, for glory and splendor (28:2). The bigdei kehunah are designed to give honor and respect. The question is whose honor are they meant to accentuate? The Ramban offers two interpretations. First he suggests that the bigdei kehunah give honor to the kohanim who wear them. Just like royal vestments give honor to a king, and cause his subjects to treat him with greater respect, so too, the bigdei kehunah make the kohanim look distinguished, so that those who see the kohanim wearing these garments will view them differently and they will treat them with greater respect.
The Gemara (Bava Kama 91b) says that R' Yochanan would call his clothing mechabdusa - things that honor me. Clothes may not make the man, but they certainly can help him make a more powerful impression. They can shape the way people view him. And this is one of the purposes of the bigdei kehunah - to bring honor to the kohanim.
But the Ramban adds another idea. He suggests that perhaps the phrase l'chavod u'l'sifares does not refer to the kohanim at all. The bigdei kehunah are not meant to bring honor and glory to the kohanim. But rather, they are designed to make the kohanim appreciate the importance of the avodah that they are performing, so that they will treat the avodah with proper respect and dignity.
This idea is echoed by the Sefer HaChinuch (#99) as well. The mitzvah of wearing bigdei kehunah is one of the places where the Sefer HaChinuch makes his famous statement that ha'adam nif'al l'fi p'oo'losav - a person is affected and shaped by his actions. When a kohen wears bigdei kehunah, he feels differently about the avodah. He takes it more seriously and treats it with greater respect. The Sefer HaChinuch adds that the same should be true of someone who wears tefillin. He should feel elevated and more spiritually focused. He should feel inspired to live with a renewed sense of purpose, to take his mission in life more seriously. Clothes don't necessarily make the man. But they can make him more aware of his mission.
Sometimes clothing is misused. People dress in fancy expensive clothing to draw attention to themselves, to cause others to treat them with honor and respect they do not deserve. This is what happened at the time of Purim. Achashveirosh threw elaborate parties to demonstrate his power and prestige. He wore the bigdei kehunah to show off y'kar tiferes gedulaso - the honor and splendor of his majesty (1:4). The emperor was wearing beautiful clothing, but the clothes were not his own. He was covering himself in the superficial trappings of majesty, but (according to one opinion) he did not really deserve the honor of kingship (Megillah 11a).
Haman also had delusions of grandeur. He wanted to be dressed in royal garments, to be treated with the honor and respect worthy of a king. And Klal Yisrael at the time played along with this charade. They attended the party of Achashveirosh and they bowed to Haman. They were willing to pay homage to the majestic charlatans who were masquerading around in borrowed clothing and undeserved glory. They were taken by the glitz and glitter being displayed in Shushan, and they had lost their ability to strip away the superficial veneer of all that fake majesty, and to appreciate that Hakadosh Boruch Hu was the only one who truly deserved their respect and their attention.
Perhaps that is why when Mordechai hears of Haman's decree, he rips his clothing, not just as a sign of mourning and teshuva, but as a symbol of the lesson he wished to convey to Klal Yisrael. Mordechai wanted to teach them not to be taken by superficial impressions. Looks can be deceiving. Only by ignoring external appearances can we perceive the truth that is lying beneath the surface. Esther and her maidservants fasted for three days (4:16). They perfected themselves through introspection and tefillah, so that when Esther finally approached the king's chamber, she was not only dressed in royal garments, but she was infused with a spirit of ruach hakodesh (Megillah 14b). Her inner purity matched the splendor and majesty of her outer appearance.
Similarly, when Haman's decree is finally annulled, Mordechai emerges from the king's presence wearing royal vestments. This posuk is a turning point of the Megillah, and one that we read aloud, not only because it signals the complete reversal of fortune for Klal Yisrael (v'na'hafoch hu), but because it presents Mordechai as a model of true majesty, one whose inner humility, modesty and purity of spirit match the splendor of his regal attire. This is the image that Chazal wished to highlight at the end of the Megillah, to show the kind of people that are truly deserving of our respect.
On Purim, we masquerade in costume to demonstrate that we appreciate Mordechai's message. All too often people fail to realize that superficial appearances are just an illusion. Only by looking past the costume and penetrating to the inner nature of people and of situations, will we gain a more accurate perception of reality, and ensure that we stay focused on our spiritual mission in life.