The presence of a mehitza (a partition between men and women) in Orthodox synagogues is normative practice, despite a wide variance in form and placement. Is there a halachic requirement to put up a mehitza in the case of a minyan outside the context of a synagogue? Defining the practical requirement for a mehitza necessitates an understanding of the source, purpose, and practical issues at the foundation of the concept. This paper purports to establish the basic premises of the law, in order to address the practical question of the requirement of a mehitza outside of a synagogue.
Sources and Purpose of Mehitza
A. What is the Source for Mehitza?
It is generally agreed upon that the source for mehitza is the Mishna in Sukka:
The Mishna describes the scene of the Beit haShoeva festival that was held on Sukkot. The Talmud comments:
The Talmud explains that the 'great arrangement' (תיקון גדול) described in the Mishna refers to building a balcony. A Baraita is brought to describe the process: At first, the women would stand in the women's court and the men were outside in the plaza and the space that surrounded the Temple area (חיל). However, this led to inappropriate behavior (קלות ראש). Next, they decreed that the women would be outside and the men inside, but problems continued. Finally, they established the 'great arrangement' of creating a balcony where the women stood above the men.
What was the purpose of the balcony, and how did it resolve the problems described in the Baraita?
The Talmud asks why it was permissible to build this balcony, given that all of the instructions for building the Temple were divine, and presumably, human additions should be prohibited. The answer is based on a verse in Zachariah that describes a eulogy given at the end of days, at which men and women congregated separately. The Talmud assumes that if in tragic times men and women are separated, there must be an even greater need for separation when the evil inclination is powerful, in joyous times.
What is the nature of the prohibition of adding to the Temple (הכל בכתב), and why isn't the addition of the balcony a violation of this prohibition?
When King David provided the set of instructions for building the Temple to his son, Shlomo, he concluded that all of the plans, which were revealed to him via Shmuel haNavi by God were 'written'.
The Hida explains that this verse invokes the prohibition of not adding to or subtracting from any aspect of the divine plans for the construction of the Temple.
Based on this injunction, the Talmud questions the permissibility of constructing a balcony. How does Rav's explanation of the verse in Zachariah solve the Talmudic question? What do we learn from this resolution about the obligation of mehitza?
Rashi explains that the reason men and women are separated in Zachariah is to prevent inappropriate behavior.
The Maharsha's interpretation of Rashi's comment is that the construction of the balcony does not violate the prohibition to add to the divine plan of the Temple, because the purpose of its construction was external, to prevent inappropriate interaction (איסורא דערוה) between men and women, and not for the purpose of changing the structure of the Temple.
The verse prescribes a necessary separation; however, the addition of the mehitza in the Temple is simply an example of this separation, and not a biblical mandate, since the mehitza was not included in the original building plans.
Similarly, the Meiri acknowledges that despite the injunction against adding to the divine plan of the Temple, the Rabbis relied upon the fact that this is merely a temporary structure to permit creating a separation in order to prevent frivolity as a result of men and women intermingling.
The Meiri suggests that the need for separation demonstrated in Zachariah was so significant, it demanded the construction of a temporary balcony during the Simhat Beit ha–Shoeva event. Both the Maharsha and the Meiri underscore the importance of separation to prevent frivolity and inappropriate behavior (קלות ראש). According to both, the balcony in the Temple was not an inherent, and therefore prescriptive, feature of the Temple, but rather a response to this external need. Thus, some form of separation is necessary, however, the balcony is simply an example of a way to address this need.
The Ahronim also grappled with the nature of the balcony in the Temple. The nature of the balcony is highly relevant to practical halacha if we are to assume that the balcony in the Temple is the foundation for the requirement for a balcony in the synagogue. This assumption will be addressed in Part II. It is noteworthy that the modern responsa, unless otherwise noted, were addressing the reality of the Reform movement, which demanded a removal of mehitzot to allow families to sit together in the synagogue. The efforts of this movement trickled into Orthodox circles as well, as communities struggled to appease their own members who were interested in such arrangements.
אגרות משה אורח חיים חלק א סימן לט
וממילא חזינן מסוגיא דסוכה דאף אם היתה מחיצה אבל כזו שאפשר לבא לידי קלות ראש יש עדין אותו האיסור מדאורייתא.
At the beginning of this teshuva, R. Moshe Feinstein argues that the obligation to erect a mehitza is Torah mandated, because he believes the construction of the mehitza in the women's court was included in the original written divine plans. There is a biblical prohibition for men and women to gather together in a way that could enable frivolity. Thus, when the first two attempts to prevent frivolity by separating men and women failed, as described in the Baraita, the Rabbis resorted to building a mehitza. This is supported by the verse in Zachariah, which attests to the need for separation even at times where frivolity is unlikely.
From R. Moshe Feinstein's perspective, the need for separation inherently mandates the need for a mehitza as demonstrated by the balcony in the Temple.
R. Yehuda Henkin, Responsa on Contemporary Jewish Women's Issues, p. 112
That is to say, building a balcony for the women as a precaution instituted by the Sages to forestall intermingling, [sic] Since this is clearly Meiri's opinion, and Rashi appears to say so as well and there is no difficulty with Maharsha's explanation [in contrast to R. Moshe Feinstein, who rejects the Maharsha's approach], the conclusion to be reached is that the gezuztra in the Temple was not of Torah origin, and consequently neither is the mehitza in the synagogue.
A mehitza is not mandated even by divrei kabbalah, in my opinion…Where is there any hint of a mehitza [in the pasuk in Zacharia]? All the verse requires is that men and women not be actually intermingled, but rather men on one side and women on the other.
R. Henkin disagrees with R. Moshe Feinstein's approach that mehitza is Torah mandated, using the collective reasoning of the Maharsha and the Meiri as the foundation for his position. While the verse in Zachariah does describe the need for separation of men and women, it does not indicate the need for a formal partition. Nevertheless, there is a need for a formal, rabbinically mandated mehitza to prevent intermingling, as will be discussed below.
B. The Purpose and Practical Requirements for a Mehitza
According to the Baraita in Sukkah 51, mentioned previously, the reason for the partition is clearly to prevent frivolity and inappropriate behavior (קלות ראש).
According to the Yerushalmi in Sukkah 23, the reason for the partition was to prevent intermingling.
The Rambam reflects possible nuances between the descriptions in the two Talmuds:
In his commentary on the Mishna, the Rambam writes that the purpose of the partition was to prevent the men from looking at the women (הסתכלות).
However, in the Mishneh Torah, the Rambam's halachic code, he writes that the partition served to prevent intermingling between men and women.
The Meiri, referenced above, writes that the reason for the partition was to prevent the frivolity that results when men and women intermingle.
The Ahronim reflect both aspects mentioned in the two different sources of the Rambam:
שו"ת ציץ אליעזר חלק ז סימן ח
חושבני שמהאמור מספיק כבר להווכח על חומר החיוב של עשיית מחיצה מבדלת בין בית הכנסת לבין עזרת נשים באופן שהאנשים לא יוכלו לבוא לידי הסתכלות.
After citing another like–minded authority (the Maharam Shick), the Tzitz Eliezer concludes that the essence of the mehitza is to prevent men from looking at women.
שו"ת אגרות משה אורח חיים חלק א סימן לט
ומוכרחין לומר שכוונתו בפירושו לסוכה להסתכלות כזאת שיכולה להביא לידי קלות ראש שהוא רק כשעומדות הנשים למטה בלא מחיצה או אף במחיצה נמוכה שהן כמעורבין. וכתב זה מחמת שסובר שההסתכלות מביאה לקלות ראש כמו שכתב התי"ט ואמנם הסתכלות האנשים בנשים מביאה לידי קלות ראש, אבל עכ"פ רק כשאפשר לבא מזה לקלות ראש שייך לאסור וכשהן למעלה אף בלא מחיצה ולמטה במחיצה גבוהה עד אחר הכתפים שאין שייך לחוש לקלות ראש לא איכפת לן בהסתכלות אף להרמב"ם בפירושו לסוכה. ואף אם נסתפק בכוונתו בפירושו לדינא אין לנו אלא מש"כ הרמב"ם בהלכותיו פ"ה מביה"ב ה"ט שהוא כדי שלא יהיו מעורבבין וכן בפ"ח מלולב הי"ב שכתב כדי שלא יתערבו אלו עם אלו והוא כמו שבארתי שבלא מחיצה גבוהה יחשבו כמעורבבין כיון שבאין מזה לקלות ראש אבל מצד הסתכלות עצמה אין לחוש.
R. Moshe Feinstein posits that the Rambam in his commentary on the Mishna in Sukka was referring specifically to men looking at women (הסתכלות) in a manner that may lead to frivolity (קלות ראש). Frivolity may only occur when there is potential for men and women to interact. Thus, the separation needn't fully prevent men from seeing women, but must prevent looking at times that may lead to inappropriate interaction.
R. Yehuda Henkin, Responsa on Contemporary Jewish Women's Issues 104-5, 107-8
But regardless, it [Rambam's commentary on Negaim 13:12] shows that sitting behind a mehitza ten tefachim high, which is the minimum height that separates reshut, is called not being intermingled. From this it can be determined that the language in Hilchot Lulav and Hilchot Beit haBechirah, "velo yihyu m'urbavin," also connotes a separation of reshut… In both cases, there was a separation of reshut between the sexes, because the Chayil and Ezrat Nashim were separate domains…. So too, throughout the Diaspora and throughout the centuries we do not find any ezrat nashim that did not constitute a separate reshut from the men's section, regardless of whether or not the women were visible.
R. Henkin understands that the Rambam in his commentary on the Mishna in Sukka was referring to men looking at women (הסתכלות) that is the result of intermingling (התערבות). Thus, in contrast to the Tzitz Eliezer, the primary purpose of the mehitza is to prevent intermingling, which can, in turn, lead to inappropriate gazing.
The Rambam's discussion of a leper entering a synagogue in Hilkhot Tumat Tzaraat 10:12 indicates that the Mishna's requirements to sit behind a mehitza that is ten tefahim high, as well as the requirements to come first and leave last, intend to prevent intermingling with others that would become impure as a result of contact with the leper. R. Henkin uses this to show that a partition of at least ten tefahim can serve as a separation to prevent intermingling. Ten tefahim is also the minimum height that delineates a separate domain (רשות). He suggests that in each of the situations described in the Baraita leading up to the establishment of the balcony, the men and women were separated in their own domain. When the women were in the women's court and the men in the plaza, and vice versa, the two groups were separated by the different domains they occupied. Therefore, R. Henkin posits that a proper halachic separation, which exists in order to prevent intermingling, must consist of a delineation of domain, which is a partition of at least ten tefahim.
Prayers, as well as other forms of praise, require focus to the extent that they would not be accepted if one is distracted. Therefore, even one's wife, toward whom there is no prohibition of illicit relations and at whom one is permitted to gaze, might cause one to lose focus or have inappropriate thoughts during prayer.
The Hatam Sofer adds the elements of illicit thoughts (הרהור) and intent (כוונה) into the discussion. Thus, the partition must serve to prevent distraction and inappropriate thoughts that might impede the efficacy of one's prayers, or other forms of thanksgiving or eulogies.
The practical implications of the distinctions between these approaches are significant:
Despite the sources presented above, there is a gaping hole in the halachic literature when it comes to the necessity for a mehitza in a synagogue. Both the Rambam and the Shulhan Arukh have sections dedicated to the codification of laws and procedures that govern synagogues. However, neither of them mention, let alone mandate, the need for a physical partition inside a synagogue. Why is there no mention of the need for a mehitza in a synagogue in the halachic codes? Through which halachic mechanism do we apply the Talmudic paradigm of mehitza to our synagogues, and under what circumstances?
This absence forces us to reevaluate the basic assumption addressed in Part I, that the balcony in the Temple is the basis for the mehitza in our synagogues today. Various approaches to this matter are found in the Ahronim.
שו"ת ציץ אליעזר חלק ז סימן ח
וזה שלא נזכר בשו"ע מדין עשיית מחיצה בין ביהכ"נ לעז"נ =בית הכנסת לעזרת נשים= הוא מפני שאז לא היתה קיימת בעיה כזאת בכלל, כי כל בתי הכנסיות היו עשוים באופן שכותל עב היה מפסיק בין ביהכ"נ לעז"נ והיתה מגעת מהרצפה ועד הגג וקול התפלה היה מגיע להם דרך חלונות קטנים או דרך חלולים חלולים, שהיו עשוים בכותל, ולא עלה על הדעת כי תתקיים בכלל בעיא כזאת אם צריכים מחיצה.
The Tzitz Eliezer explains that there was no reason for the obligation to erect a mehitza to be codified, since there was never a question of not putting up a partition. All synagogues had a thick wall that served as a partition between the synagogue and the women's section, and no one would have thought to do otherwise.
The Tzitz Eliezer assumes that the mehitza, whose purpose was to prevent gazing at women (הסתכלות), was a given reality in all synagogues. While this explanation lacks definitive proof, the strength of this assertion demonstrates that the author never experienced anything to the contrary. Nevertheless, the question of the relationship between the balcony in the Temple and the mehitza in a synagogue remains unanswered.
מאמרי הראי"ה עמוד 514
אבל הכל מודים שתמיד היו מובדלין האנשים והנשים זה מזה בביהמ"ק. וזאת היא חובה ומשמרת הקודש שקבלו כן אבותנו הקדושים לעשות ג"כ בבית מקדש מעט בבתי כנסיות שלנו.
R. Kook invokes the idea from the Talmud in tractate Megilla that a synagogue is considered a small Temple (מקדש מעט). As such, the synagogue requires similar laws, customs, and decorum to those found in the Temple. Prior to this excerpt, R. Kook explains that, based on the Rambam, there was a permanent balcony all year round in the in the women's court, and in preparation for Simhat Beit haShoeva another layer of separation was added to prevent frivolity. As such, he posits that the existence of a permanent women's section in the Temple is an obvious paradigm for the layout of all synagogues.
R. Kook offers a genuine connection between the Temple and the synagogue based on the concept that the synagogue is a 'small Temple.' Since he is of the opinion that the balcony was part of the design of the Temple, it follows that it should be part of all synagogues.
שו"ת אגרות משה אורח חיים חלק א סימן מא
ובשעת תפילה ממש אפשר גם לפ"ז הוא מדאורייתא כיון שמזכירין אז שם שמים ודברי תורה וקדושה. אבל מהספד דלעתיד לבא שלמדין משם משמע דהוא איסור בכל מקום שמתקבצין שם לאיזה חיוב להתקבץ ובלא צורך חיוב קבוץ אף במקדש מותר כהא דחנה שהתפללה במקדש אצל עלי
R. Moshe Feinstein's approach to mehitza focuses on the type of gathering rather than a particular place. He thus bypasses the assumption that the design of the Temple dictates the design of our synagogues. He suggests that the obligation to have a mehitza applies only at times of communal gathering. In his responsa on this matter, he distinguishes between public and private gatherings, as well as obligation versus voluntary action. These details will be discussed further in the next section. Neither prayer nor a synagogue in and of themselves require a mehitza, as we see from the case of the biblical Hannah who prayed beside the priest Elli in the Temple. Thus, while by its communal nature a synagogue should have a partition for use during times of gathering, the issue of mehitza is not limited to this type of venue.
הרב צבי יניר, דף קשר ז (ישיבת הר עציון), 573-568
אין שום מקור לחיוב מחיצה בבית כנסת, לא מהתורה ולא מדרבנן, וזהו מנהג בלבד. לא שייך לדבר על מהות המחיצה שהייתה בבית המקדש, כי המנהג מחייב בסופו של דבר כפי המציאות בשטח. ממילא גובה המחיצה ושקיפותה תלוי במנהג.
R. Yanir surveys the halachic literature, and suggests that the practice of separating men and women with a partition is a "grassroots custom". As such, the particulars of such a partition are dependent on local custom. Thus, while the assumption that the balcony in the Temple is the basis for our synagogues today stands, the parameters of such a partition are based in local practice.
R. Yanir posits that the need for separation and the mode of separation are two different issues. While the need for separation is explicit based on the aforementioned sources, the mode of separation is dependent upon cultural factors and thus can legitimately vary in different situations, time periods, and locales.
Finally, we can attempt to answer the original question by addressing the particular issues involved in the requirement for a mehitza. To reiterate, in the case of a minyan outside of the context of a synagogue, is there a requirement for a mehitza?
A. An Incidental Minyan
Is an occasional minyan different from a regular gathering? For example, a one–time minyan at an airport as opposed to a nightly Maariv minyan in the entrance to an apartment building?
שו"ת אגרות משה אורח חיים חלק ה סימן יב
שאלת אם צריך מחיצה כשמתפללים במקום שאינו קבוע לתפלה, למשל, בבית אבל רח"ל. אם צריכות הנשים לילך לחדר נפרד, או שדי בהפסק אוויר. ונראה שלדינא הנשים בבית אבל צריכות ללכת לחדר אחר. והטעם דבית אבל הוי מקום שפתוח לרבים, שצריך בו מדינא תמיד הפרדה בין הנשים לאנשים, וכל שכן בשעת תפילה, כמבואר בתשובתי בא"מ או"ח ח"א סימנים ל"ט-מ"א. אבל אם למעשה הנשים אינן מסכימות לעזוב את החדר, נחשב זה לאקראי, ואין להמנע מלהתפלל מחמת זה. אבל בבית חתן מדינא אין צורך במחיצה, שאינו פתוח לרבים, אלא רק לבני המשפחה. לכן די בכך שילכו האנשים המתפללים לזווית אחת שיוכלו לכוין שם, ושם יתפללו.
R. Moshe Feinstein addresses the situation of a minyan in a shiva house, a house of mourning. Since the house is open and anyone is free to enter at this time, it is considered a public gathering place, and ideally, women and men should be in separate rooms, especially for prayer. However, he adds that if the women do not agree to leave the room, the minyan can take place there, as it can be considered a temporary occasion.
R. Moshe applies two principles in his ruling that are rooted in his general approach to mehitza:
- The venue is considered a place of public gathering, and hence requires a mehitza (note that he requires a separation in general, all the more so during prayer).
- Ex post facto, the minyan can occur even in a room with women present, since it is a temporary / one–time situation.
R. Moshe contrasts this situation with a minyan at the house of a bridegroom (בית חתן/שבע ברכות), which is considered a private event. Thus, the men can congregate in a corner of the room and pray there. It is noteworthy that R. Moshe does not seem to address a situation where women intend to daven with the minyan, rather the situation described is a minyan where women are present in the room.
By extension of his reasoning, and using the paradigm of Hannah, it would seem that women could pray concomitantly but in a separate area of the room. However, R. Moshe offers a slightly different approach here:
שו"ת אגרות משה יורה דעה חלק ב סימן קט
הנה בדבר המיטינגען של הסאסייטע שבאין לשם אנשים ונשים לשוחח ולהווכח ולהחליט בעניני חול של הסאסייטע, ותיקנו שבכל מיטינג ילמוד אחד מהחבורה איזה דבר תורה בפסקי דינים משלחן ערוך או בדברי מוסר ויראה, הוא תקנה טובה ויישר כחכם. ובדבר הנשים אם יכולות להיות שם גם בשעת הלמוד כמו שהן נמצאות שם בשעת השיחות ודיונים בעניני חול, או שצריכות לצאת לחדר אחר, הנה דברי תורה ומוסר לא גרעי מעניני חול וכיון שאין אתם מחמירים עליהן שלא לבא להמיטינגען כמו כל הסאסייטעס שבמדינה זו שגם הנשים משתתפות בכל הדברים, אף שאין ידוע הטעם שמקילין במדינה זו בפשיטות אבל כיון שמקילין אין שום טעם שיצאו בשעת הלמוד כי גם נשים צריכות לידע דיני התורה וטוב להן שישמעו דברי תורה דינים ומוסר כדאמרו חז"ל בהא דמצות הקהל ריש חגיגה נשים באות לשמוע. וכן טוב שישמעו בכל מקום דברי תורה. אבל אם יגיע זמן תפלת מנחה או מעריב וירצו להתפלל שם יצטרכו הנשים לצאת לחדר אחר ולא בחדר שמתפללין שם האנשים. ידידו, משה פיינשטיין.
It is R. Moshe's position that in the context of a meeting, where it is customary for there to be a dvar Torah, women and men may participate together. However, in the end of his responsa he writes that if it is time for communal prayer and the women wish to pray, they should go into another room and not be present in the room in which men are praying.
This seems to contradict the previous response, since one would assume a meeting is a private event analogous to the house of a bridegroom, in which case, the men should be permitted to pray in one localized area, while the women are present.
One possible explanation for this apparent contradiction is that R. Moshe is discussing a situation where people are already being intentionally lenient. He argues that since in the modern world men and women work together and attend joint meetings, there is no need to be excessively stringent when someone gives a dvar Torah and exclude women from participating in a meeting. However, perhaps he felt it necessary to assert that the women leave the room for prayer, in contrast with the house of a bridegroom, to demonstrate that this is not an ideal system. Furthermore, R. Moshe's approach assumes that the purpose of the mehitza is to prevent frivolity. It is reasonable to understand frivolity as encompassing both flirtatious behavior as well as lighthearted, casual interaction. A workplace, in contrast with the house of a bridegroom, may be more prone to such casual interactions, and as such, he felt the need to mandate that women should go into a separate room.
From these responsa, it seems that a public gathering, whether as a regular occurrence or a one–time event, should require a mehitza if women are present. However, if this is not possible due to the women's reluctance to leave the room, the leniency of a "one–time" occasion may be applied to allow the minyan to proceed in their presence. Regarding a private gathering, it seems that R. Moshe would allow men to pray in the presence of women, from the outset – lehatchila, although his response to mixed business meetings casts some doubt as to his position on this category.
R. Yehuda Henkin, Responsa on Contemporary Jewish Women's Issues p. 124
Outside of a synagogue a mehitza is mandatory when two conditions are met: first, both the men and the women intend to participate in the prayers, and second, the place is being used at the time solely for prayer. These are the circumstances regarding the eulogies described in Zachariah 12:12, and where these conditions do not apply, a mehitza is not required. For this reason no mehitza is required in a wedding hall when a minyan of men gather in one corner, both because the women do not participate and the hall is not being used exclusively for prayer.
R. Henkin offers two criteria based on the verse in Zachariah, both of which are required in order to mandate the necessity of a partition. R. Henkin presumes that a eulogy is analogous to prayer, although it is unclear from this specific paragraph whether or how he would apply these criteria to other events, such as a huppah at a wedding or a dvar Torah. Nevertheless, for the purposes of our question, neither a regular minyan in a building lobby nor a one–time minyan at an airport would require a mehitza, since the venue is not used solely for the purpose of prayer at that time.
B. The Routine or Occasional Presence of Women
Would the regular presence of women differ from an occasional presence?
שו"ת אגרות משה או"ח חלק ה סימן יב
שאלת אם צריך מחיצה לחצוץ רק בפני אשה אחת או שתים. שהנה באג"מ ח"א א"ח סימן ל"ט בסופו, הבאתי ראיה מקידושין נ"ב ע"ב תוד"ה וכי אשה בעזרה מנין, שאין חיוב מחיצה להפסיק לפני כמה נשים בלבד. וצריך לבאר עד כמה נשים אין צריך מחיצה. כגון בבית אבל, או בבית מדרש שמתפללים שם בימי חול ובמנחה בשבת, שאין שם מחיצה, האם מותר להניח שכמה נשים יכנסו וישבו בסוף החדר. והנה בכל הדורות נהגו שלפעמים היתה נכנסת אשה ענייה לבית המדרש לקבל צדקה, או אבלה לומר קדיש, וההלכה למעשה בעניין זה צריכה עיון ותלויה בהרבה עניינים. ומכל מקום נראה שבבית מדרש שבכל שבת תרצה אפילו אשה אחת לבוא למנחה בקביעות, שאין להקל להתפלל בלא מחיצה, ורק באקראי אפשר להתיר. ואפשר להתיר, באקראי, רק עד ב' נשים ולא יותר. והנה יש ראיה, כעין שהזכרת, שלדינא אפשר להניח לאשה אחת להכנס לבית המדרש, מן הדין בשולחן ערוך או"ח סי' רפ"ב סעיף ג' דאשה עולה למנין שבעה קרואים.
R. Moshe discusses whether a mehitza is required if only a few women are present. He brings two examples, a house of mourning and a Beit Midrash – a study hall. He believes if there is a regular presence of even one woman, a mehitza is required. Leniency only applies on occasional situations, in which only one or two women may happen to pray in the back of the room. He bases his answer on two sources:
- The Talmud in Kiddushin 52 discusses whether a woman can be present in the Azarah – the highest level courtyard in the Temple. We see from here that women can, in fact, be present under some circumstances, and there is no indication that a mehitza is necessary.
- The Shulhan Arukh Orah Haim 282:3 states that a–priori a woman may receive an Aliya l’Torah, and she needs to access the men's section in order to do so; therefore there is no evidence here that there is requirement for a partition
Despite the fact that a minyan in a Beit Midrash, an airport, or a building lobby is considered a public gathering, if such a gathering is not usually attended by women, it would not require a mehitza if one or two women do happen to attend.
R. Yehuda Henkin, Responsa on Contemporary Jewish Women's Issues p. 116, 124
A Rabbi asked me about a synagogue that had a proper ezrat nashim in a balcony, but below in the women's section there was a bench for elderly women who were unable to walk up the stairs. May he pray there, and was it proper to have such an arrangement to start with? ... In my opinion one should not initiate such an arrangement, but bedieved and on an irregular basis the presence of individual women in the men's section does not invalidate the prayers…If they come regularly, however, a mehitza should be built around their bench.
R. Henkin's conclusion is similar to that of R. Moshe Feinstein above, and in his explanation he, too, cites the Talmud in Kiddushin, and brings the issue of women reading the Torah as basis for his ruling.
R. Henkin's approach to mehitza is rooted in the prevention of intermingling, which is accomplished by creating a separate domain. Ideally the women's section should be a separate entity, and as such a bench in the back of the men's section would not suffice. Therefore, he concludes that if the women are a regular presence in the men's section, a separate domain should be constructed for them by erecting a partition.
Both R. Moshe Feinstein and R. Henkin permit the presence of women in a minyan if it is an occasional occurrence. While R. Moshe clearly writes that this is permissible only for one or two women, R. Henkin specifies only "a few" without mentioning a number.
C. The Size and Purpose of the Gathering
Does the size or purpose of the gathering affect the need for a mehitza? For example, a city–wide minyan in a public plaza, in contrast with a private minyan in a house?
In the context of a discussion about yihud, the prohibition for a man and a woman to be alone, the Talmud anecdotally describes how Abaye and Rava would set up barriers between gatherings of men and women, one out of jugs and the other of reeds. Rashi explains that they would do so during a sermon or a huppa at a wedding ceremony, so that if a man crossed into the women's section the partition would rustle and make noise. Thus, it served as a prevention of yihud. Why was this necessary? Avin answers: the wound of the festival, on which Rashi explains: while in public gatherings all year round there is a certain degree of concern about yihud, the risk is much higher on a holiday when men and women gather together to hear sermons, thereby interacting with each other.
This text underscores the possibility of frivolous interaction between men and women at times of public gathering. Since holidays are a prime time for socializing, in modern times as well, it seems that we should be careful to encourage proper interactions and limit improper ones. However, this text appears to be a descriptive social commentary rather than a prescriptive halachic statement. As such, it is not mandating a mehitza, but rather illustrating the precautionary measures that were taken during such occasions.
The Shulhan Arukh, based on the Rambam in Hilkhot Yom Tov 6:21, requires the courts to employ guards to watch the gardens and orchards so that men and women would not gather there to eat and drink together, leading to inappropriate behavior. Similarly, they would guard the people from intermingling in houses and drinking frivolously. The Mishnah Berurah adds that we are always concerned about these interactions, and should generally rebuke people when possible, but holidays lend themselves to worse behavior.
We see that the halachic codes are similarly concerned that the holidays lend themselves to frivolity, and as such they mandate active supervision over public gatherings. By extension, R. Yanir suggests that these sources provide a basis for the assumption that a separation is needed at all public gatherings, although he rejects this idea in his conclusion. R. Moshe Feinstein's assertion that a mehitza is needed at all public gatherings may be rooted in this idea, despite the fact that he does not base his reasoning on this particular halachic sugya. It is noteworthy that these last sources do not address mehitza specifically, but rather just the need for separation.
Thus, we can return to the question above: Does the size or purpose of the gathering affect the need for a mehitza? It seems based on the sources above that a large, public gathering has a unique status requiring supervision and separation due to the fact that it lends itself to frivolous behavior. However, even without this qualification, according to both R. Henkin and R. Moshe Feinstein, a minyan at a large public gathering, even outside the forum of a synagogue, would require a mehitza. According to R. Moshe Feinstein, any public gathering for prayer requires a mehitza. According to R. Henkin's approach, even an outdoor plaza would require a mehitza because both men and women are participating in the prayer service, and because the venue is used exclusively for the service. Perhaps one might argue that the presence of many passersby who walk through without participating would negate this second factor. Nevertheless, the sources above underscore the importance of separation at a large, public gathering, and it seems logical to err on the side of caution in the case of a minyan in a plaza.
To conclude, this paper presented three fundamental issues necessary for addressing the question of the need for a mehitza outside the context of a synagogue.
The premise for answering this practical question is a discussion of three essential issues: (a) the relationship between the requirement to separate men and women and the means of doing so; (b) the purpose of the separation of men and women, and (c) the connection between the practices in the Temple and the synagogue.
Despite the practical differences among the positions presented in this paper, we are left with an enduring understanding of the need for separation under certain circumstances. The requirement and degree of separation are affected by the particulars of the scenario, including whether the gathering in that space is regular or occasional, if the event is public or private in nature, and whether and in what number men and women may be praying together.