Why do we wear disguises on Purim, sometimes appearing as non-Jews?
The Gemara (Megillah 12a) asks why the Jews in the generation of Mordechai and Ester deserved to be (almost) destroyed. Rabi Shimon bar Yochai answers that they erred by enjoying Achashverosh’s feast. This answer raises another question. If this is the case, then only the Jews in Shushan should have been held responsible; what made the Jews who lived everywhere else guilty as well? The Gemara explains that they all bowed down to Nevuchadnezzar’s idols. Then why weren’t they actually punished? Why did Haman fail to destroy them?
One of the early uses of disguise is in Sefer Bereishit when Yaakov dresses himself in Eisav’s clothes to receive the Berachah from his father. Just as Yaakov at that time looked evil, but was holy on the inside, so too, during the time of Purim, the Jews were righteous on the inside and were only pretending to worship idols. Hashem responded similarly, by allowing Haman to threaten the Jewish people but ultimately stopping him from succeeding. This is one way to explain the custom to wear disguises on Purim.
Another source is derived from the Pasuk (Devarim 31:18), “VeAnochi Hasteir Astir Panai BaYom HaHu,” “And I shall surely hide My face on that day.” Chazal explain that Hasteir, to hide, is phonetically similar to the name Ester. Therefore, on the day of Ester we hide our faces.
Haman, the enemy of the Jews in his generation, descended from Amaleik. Though there are many differences between Amaleik and Bnei Yisrael, there is at least one similarity – both Bnei Yisrael and Amaleik have a history of disguising their true identities. Eisav, the ancestor of Ameleik, dressed nicely, spoke smoothly, and pretended to be pious. The Torah, however, teaches us in Sefer Bereishit that “there was game in his mouth” (25:28), meaning that his nice words did not match his intentions. He was hiding the fact that, behind the good characteristics, he was actually wicked. When Yaakov dressed up as Eisav, he was doing it for the right purpose. Even his father could not recognize that Yaakov was truly a Tzaddik until Rivka pointed it out to him. At that point, Yitzchak bestowed the Berachot upon Yaakov, who was the only one truly worthy of receiving them. On Purim, may our internal good intentions earn us Hashem’s blessings.
-Adapted from The Book of Our Heritage