When you walk the streets of Jerusalem, or the Jewish area of any town in the run up to Purim, you see the shop racks full of costumes, the masques of masquerade hanging in display, adorning arcade mannequins. “Mordechai” and “Esther” joust for attention with mutant ninja turtles and Spiderman; Kallah (bridal) dresses and “Torah scrolls” alongside fairies and Winnie the Pooh.
Dressing up on Purim is a long-standing custom; the earliest record is found in the writings of the Mahari Mintz, a late 15th century Italian Rabbi and scholar. He writes that on Purim it is permitted for a man to dress up as a woman and vice versa, and it is clearly implied that this is a custom that is well established in his day.
Which begs the question: Why do we wear costumes on Purim?
There are a number of different reasons. A mask and costume hide the identity of the wearer. From the outside not only can you not tell who the individual wearer is, you don’t have any insights into their nature whatsoever. Maybe behind the mask, no matter how far they appear to be from Torah, is a Jew, a family member, “one of the tribe”.
One of the deeper reasons for this custom is that the entire miracle of Purim was clothed in natural happenings. The events of the Purim story happened over a period of years and are seemingly unconnected. There isn’t even an explicit mention of
Within the Megillah there are a number of “dressings up”. Vashti remains attached to her attire despite the demands of Achashverosh. Esther doesn’t reveal her people — no one knew where she was from nor realized she was Jewish. People who saw her thought she was from their (foreign) nation. Mordechai wore sackcloth in mourning for his people and was later dressed in the clothes of the king.
To take another approach, what is at the root of Amalek’s hatred of the Jewish People? Amalek is the direct descendant of Esav, and it is with Esav that we first encounter the idea of clothes concealing that which is within. Esav is the archetypal “wolf in sheep’s clothing”. His outward behavior was that of a tzaddik, while his inner drives were pure evil. In contrast, Yaakov’s righteousness was so concealed that even Yitzchak didn’t recognize it until Rivka revealed it. Yitzchak was going to give the special blessing to Esav. At his mother’s instigation Yaakov, wearing Esav’s clothes, preempted Esav and went to Yitzchak with the food that Rivka had prepared. On a superficial level, Yaakov’s behavior seems deceptive. On Purim we dress in different clothes to show that Yaakov did not commit a sin, and even though he wore the garments of Esav, Yaakov is indeed “blessed”.
On a more practical note one of the mitzvot of the day is giving charity to the poor. Receiving charity can be devastatingly embarrassing for someone. When they are in fancy dress, however, no one can see their face, and they are not recognized, thus sparing the embarrassment.
Finally, as we all know, dressing up is fun and adds to the simcha and the joy of the Purim celebrations, and Purim is a day for celebration!