I
"Hashem spoke to Moshe in the ohel moed" (Bamidbar 1:1), the private tent of meeting. Hashem had spoken to Moshe earlier from the burning bush, in Mitzrayim and in Sinai. Once the ohel moed stood, Hashem said: Tznius (modesty) is beautiful, as it says (Micha 6:8), "to walk humbly im (before) your G-d", and He spoke to Moshe in the ohel moed. And so said Dovid (Tehillim 45:14) "Every honorable bas melech (princess) dwells within." Bas Melech refers to Moshe...Hashem said, such is My honor, that I will speak from within the ohel moed (Bamidbar Rabba 1:3).
While the medrash quotes the passuk in Micha to explain Hashem's behavior, the passuk seemingly refers to the tznius of man before Hashem, not that of Hashem himself. The medrash's use of the passuk indicates, as the peirush Maharzu explains, that "im" does not mean "before," but rather "with." Man must be tzanua with Hashem, Who modeled tznius by speaking from the ohel moed.
The peirush Maharzu offers two explanations of the reference to Moshe as bas melech. First, Moshe may be the king (see Rashi Devarim 33:5), and Torah is the private princess, compared to hidden thighs (Shir Hashirim 7:2); just as the thigh is kept private, so too the words of Torah should be studied in private (Moed Katan 16a,b). Alternatively, bas melech may refer to Moshe, since he was raised by bas Paroh, king of Egypt (Tanchuma). Moshe, the greatest human being in history, is thus praised for his tznius, which is undoubtedly related to his incomparable humility (Bamidbar 12:3).
The phrase "tznius is beautiful" is found once again in the context of mattan Torah. Before giving Moshe the second luchos, Hashem told him, "No man shall ascend with you [up the mountain]" (Shemos 34:3), on which Rashi comments, "The first luchos, because they were given with fanfare and great sound and in a throng, were affected by the evil eye. There is nothing more beautiful than modesty."
Why, indeed, were the first luchos given with such great publicity? Because the revelation at Sinai is the cornerstone of our belief in Hashem and the Divinity of the Torah (Rambam, Hilchos Yesodei Hatorah 8:1). Hashem, Who models tznius to the point of being invisible, deemed it necessary to be uncharacteristically demonstrative so that we shall believe in the Divinity of the Torah forever (Shemos 19:9).
On Shavuos, the anniversary of matan Torah, we encounter tznius again in the story of Rus (see Rus Rabba 4:6). "To whom does that young woman belong" (Rus 2:5)? Since he saw her beautiful deeds, he asked about her. All the women bend down and gather (grain), thereby revealing the legs and highlighting the shape of the body. But she (Rus) sat down and gathered, lowering her entire body in a modest way (Etz Yosef). All the women flirted with the farmers, but she behaved modestly (matzna'as atzma).
The exemplary modesty of Rus, in both her dress and her behavior, was noticed by Boaz. As a result he married her, and she merited to be the mother of royalty, the ancestress of Dovid, and ultimately, the Moshiach.
The legitimacy of this marriage was questioned. Some said that all Moavite converts, including Rus, are prohibited (Devarim 23:4). Others argued that this restriction is limited to male converts. What is behind this dispute?
The Midrash (see also Yevamos 76b) refers to the Torah's reason a Jew may not marry a Moavite, "Because of the fact that they did not greet you with bread and water in the road when you were leaving Egypt" (Devarim 23:5). The Ramban explains that since Avraham saved Lot, the ancestor of the Moavties, their debt of gratitude to Avraham's descendants should have motivated them to greet Am Yisroel. Their display of ingratitude resulted in the marriage prohibition. Even though we would never expect the Moavite women to greet the Jewish men, they are prohibited since they should have greeted the women of Am Yisrael.
Remarkably, the Midrash, which begins by extolling Rus' modesty, concludes that her permissibility (and that of all Moavite women) is based on precisely the same notion of modesty: based on the aforementioned reference to a princess dwelling within, the way of a woman is not to go out towards wayfarers, even women, to bring them bread and water.
Hashem requires modesty from all people. The additional modesty expected of women applies to non-Jews, such as Moavites, as well (see, however, Maharshal Yevamos 77a). Indeed, Hashem's first command to mankind implies that a woman should not be a gadabout (Rashi, Breishis 1:28).
II
Notwithstanding the immutability of the Torah's principle of modesty and its particular application to women, the precise details are subject to communal standards which often change and/or vary from place to place. This is true regarding some parts of a woman's body which must be covered (Shulchan Aruch Orach Chaim 75:1). Nonetheless, there are other parts which must be covered regardless of communal standards.
The Mishna Brura draws the line at the elbow and the knee (75:2). Some interpret "shok" (Berachos 24a) as the calf (since the thigh is called yerech), and include it in objective erva (see Chazon Ish Orach Chaim 16:8). Yet others imply that since the requirement to cover the arms and legs is das Yehudis (Kesubos 72a), i.e. a custom of Jewish women (Rashi), it may be subject to change (see Kaf Hachayim 75:2, Igros Moshe Even Hoezer 1:69). Sha'ar Hatziyun 75:5 disagrees.
However, a woman's torso is certainly ervah (see Rambam Krias Shma 3:16), and must be covered. Unfortunately, many otherwise observant women follow fashions, such as very low necklines, which expose the flesh inappropriately. Women who wear tight-fitting clothes which explicitly delineate a woman's figure are also in violation, as the Midrash, contrasting Rus and the other women, implies (see Kuntres Dinei Malbush Nashim page 12, 13).
The distinction between variable details and timeless principles is not limited to dress. It applies, in a more complex and nuanced way, to the definition of tznius in the Torah society. For example, public speaking by a woman in front of mixed audiences is commonplace in some circles and unheard of in others. For many parts of Torah society, it depends upon the place, the occasion, and other factors. Similarly, interaction between men and women, another subject of the Midrash about Rus, is also dependent upon local custom (Beis Shmuel 62:11, see Otzar Haposkim there). This includes separate seating, entrances, mechitzos, etc. Here, too, context is clearly critical.
It must be noted that the opposite of tznius is pritzus (Kesubos 3b), a term linked to one who breaks a fence (Koheles 10:8), and different communities legitimately build their fences in different places. As such, a garment, speech, or event can be labeled as pritzus in one place, but be acceptable in another.
However, even though the details can change, the Torah principles are eternal. General society rejects the Torah's inherent emphasis on modesty and its distinction between men and women. In particular, egalitarianism is antithetical to the Torah's principles of modesty and gender distinction (see Igros Moshe Orach Chaim 4:49). Even in changing times, the Torah has established absolute gender specific parameters regarding a woman's public role which can not be included in the category of communally dependent details. Even if sincerely motivated, efforts to impose external values on the halachic system, instead of interpreting and applying timeless halachic values, are unacceptable.
Parashas Bamidbar and Shavuos coincide with the summer season, when the lack of tznius in dress is most flagrant. The principles of modest behavior, for men and even more so for women, do not depend on the time or the season. They are Divine principles derived from Hashem's choice of the ohel moed, the inwardness of a princess, Moshe, and the Torah, and the modesty of Rus. Even as details vary, we must practice and accept the eternal fundamentals of Torah - na'aseh venishma.