It is written in the Torah (Devarim 22): “A man’s vestments shall not be on a woman and a man shall not wear a woman’s clothing”. We learn from here that a man may not wear women’s clothing and similarly, a woman may not wear men’s clothing. This is also elaborated in the Shulchan Aruch, Yoreh De’ah (Chapter 156) that a man may not do things that usually constitute beautification for women, such as looking in a mirror, for looking in a mirror is an action designated for women and men do not usually do so; therefore, it is forbidden for a man to look in a mirror. Nevertheless, the Poskim write that in a place where it is common for men to look in the mirror as well, there is no prohibition to do so, for then it is no longer considered a beautification process specific to women. Thus, nowadays, we rule leniently and it is indeed permitted for a man to look in the mirror. However, regarding actually wearing women’s garments there is no room for leniency, for this is a beautification specific to women alone.
However, some Ashkenazi countries had the custom that men would wear women’s clothing and vice versa on Purim. Hagaon Mahari Mintz (page 31a) writes that the reason why they would customarily be lenient about this is since on Purim everyone acts this way, therefore, on this day these articles of clothing are not specific only to men or only to women and there will not be any prohibition involved. This is similar to what we have written above regarding the permission for men to look in the mirror nowadays. He adds that since people are not doing this to transgress a prohibition, G-d forbid, rather only in the joyous spirit of Purim it is not prohibited and he brings reasoning for his opinion. The Rama, in his notation on the Shulchan Aruch, writes very similarly to this.
Nevertheless, the opinion of most Poskim is that one may not be lenient regarding any prohibition, even if it is done in the joyous spirit of Purim. Similarly, Rabbeinu Eliezer MiMetz writes in his Sefer Yere’im: “Even in a temporary and joking manner, a man may not wear women’s clothing and vice versa as the Torah has not differentiated between wearing them in a permanent or temporary manner. I felt the need to write this because I have seen men wear women’s clothing at wedding banquets.” One can infer from his words that one may not be lenient in this matter at all, even if is done in a joyous spirit, and doing so touches on grave Torah prohibitions.
The Rambam writes similarly in one of his responses, “regarding the custom that some had that the bride would wear a man’s hat and take a sword in her hand and parade this way in front of men and women amid song and dance, one should not think that just because she is a bride the Torah prohibition involved in this abominable act is any less severe, and this was even the custom in Egypt until we came and uprooted this custom and eradicated its memory. There was a similar custom where the groom would go to a female make-up artist to make him up like a woman, and this is also considered ornamentation of a woman which is forbidden for a man to do.” The Bayit Chadash brings the words of the Sefer Yere’im and writes that the words of the Yere’im must certainly have been hidden from the holy eyes of the Rama and one must be stringent in this matter by a wedding banquet or on Purim day. Maran HaChida agrees to this opinion in his Sefer Shiyurei Beracha (Chapter 182) and he quotes the Rambam’s response we have mentioned above. Maran Harav Ovadia Yosef Shlit”a also rules this way in his Responsa Yechave Da’at, and he brings many other great Acharonim who rule this way as well and speak harshly against those who act leniently in this matter. Maran Harav Shlit”a concludes his response as follows: “These words must be told over in a pleasant manner in order for people to accept them.”
It seems that parents are obligated not to dress their children in clothing belonging to the opposite gender as per the Mitzvah of Chinuch (proper Torah education) just like they are obligated to distance their children from other Torah and Rabbinic prohibitions.
In general, one must be extremely careful not to act in a frivolous or immoral matter on the day of Purim, especially in a place where non-religious Jews reside. Let us now relate some interesting anecdotes regarding Hagaon Harav Avraham Yitzchak Ha’Kohen Kook zt”l, late Chief Rabbi of Israel.
In the year 5695 (1935), many yeshiva students who studied in Jerusalem lived in Tel Aviv. On the eve of Purim of that year, Hagaon Harav Kook posted a sign at the entrance of the yeshiva which read as follows: “I hereby firmly request from all of the students of our holy yeshiva that no one go to Tel Aviv under any circumstances on the 14th and 15th of Adar to celebrate Purim.”
The reason for this was because in those days, a “Purim Carnival” was held in the midst of Tel Aviv, which resembled a truly non-Jewish practice. The celebration entailed all sorts of immodest activities which were repulsive to those who feared Hashem. Although the coordinators of the event were non-observant, they nevertheless tried to preserve some semblance of modesty during this party. From the year 5687 (1927), this carnival began hosting a “Queen Esther Pageant,” exactly the way the wicked King Achashverosh had done. This ceremony quickly became the main event of the annual carnival.
For this reason, Hagaon Harav Kook waged a spiritual battle against this despicable violation of Torah and modesty and forbade his students from going to Tel Aviv on the days when the party was held. Eventually though, thank-G-d, Hagaon Harav Kook’s words were accepted and this disgraceful ceremony was discontinued in the year 5693 (1933).
We see how much this righteous man fought in order to restore religion and Halacha observance to the maximum and to influence even those that were far from Torah and Mitzvot observance to celebrate the holiday of Purim amid great sanctity as this extremely lofty day deserves.
Summary: Girls/women may not wear boy’s/men’s clothing and boys/men may not wear girl’s/women’s clothing even if this is done in celebration of the joy of any particular Mitzvah. The guidelines of sanctity and modesty must be safeguarded during the days of Purim. Those who heed us shall dwell securely.