(יח) וְאָנֹכִ֗י הַסְתֵּ֨ר אַסְתִּ֤יר פָּנַי֙ בַּיּ֣וֹם הַה֔וּא עַ֥ל כָּל־הָרָעָ֖ה אֲשֶׁ֣ר עָשָׂ֑ה כִּ֣י פָנָ֔ה אֶל־אֱלֹהִ֖ים אֲחֵרִֽים׃
(18) And I will surely hide My face in that day for all the evil which they shall have wrought, in that they are turned unto other gods.
Ba'al Shem Tov
“It is a mitzva...to dress up on Purim” - Indeed, it is a great mitzva, because in this way one cannot tell the noble man from the poor. And therefore they [the rabbis] instituted the mitzvah of gifts to the poor on Purim, because when people dress up, the mitzvah of tzedakah may be performed in its most appropriate manner [כתיקונה]. One does not know then to whom they give, and the one who receives does not know from whom they receive, and thus no one is embarrassed to appear needy and dependent on human kindness. This is the best manner of anonymous giving, when one gives while in costume to someone else in costume.
Purim invites us to set aside a time in which we completely reverse our wardrobe, which in turn reverses our identity. It is an invitation to...cross and reverse all the other dichotomies and uniforms of our lives as well. On Purim we are using clothes against themselves, to deny their power to box us in, and simultaneously to redeem us from needing redemption...Purim...makes us wonder if there is an "authentic self" at all, or whether it is all just endless masks upon masks.
On the surface, it seems that Purim involves an escape from reality...Purim provides us with the hope that the garments we put on that seem only to mask our present realities can reveal the deep-seated consciousness of our potential for change, our ability to bring happiness and fulfillment to our lives.
...we may ask what lies beneath a story that intimates the absence of God and meaning, and the holiday of Purim, which is about frivolity and play. Underneath the garment of the story is perhaps a glimpse of the existence of a force in the universe that can help us move beyond who we are and what our lives presently are, and enable us to become who we aspire to be.
Cohen, D. N. J. (2012). Masking and Unmasking Ourselves: Interpreting Biblical Texts on Clothing & Identity (1 edition). Woodstock, VT: Jewish Lights.