Halachot involving proper clothing tend to be more subjective than most areas of Halacha. However, the discussion must begin with an examination of the halachic philosophy and standard situations. We have previously written about wearing short pants for davening, with a focus on the chazan,[1] and we refer you there for additional sources.
When one davens, he stands before HaShem and, accordingly, should dress respectably.[2] The Shulchan Aruch[3] writes that this includes covering one’s legs, when this is how people dress before important people. The Mishna Berura[4] adds that one should wear a hat, explaining that this is the way people dress is public. (In some circles, this is still true; in others, it does not apply at all.)
Even in surroundings in which one should cover his legs, the requirement is not as far-reaching as parallel requirements. One’s tefilla is invalid b’di’eved only if his genitalia are uncovered[5] or if there is no external separation between his heart and genitalia.[6] There is some question as to whether it is better to daven or to refrain from davening if one is not able to cover his chest.[7] In the case of other “improper attire,” including short pants, one may daven. However, the Shulchan Aruch[8] writes that when it is possible, one must be properly dressed.
Rav Ovadia Yosef[9] rules that in places where shorts are commonplace (e.g., kibbutzim), it is permitted to daven in shorts.[10] We accept that approach, which leads to the subsequent challenge of determining whether short pants are commonplace enough in specific venues.
Does Shabbat change matters? We certainly find halachic areas in which it does. For example, Shabbat raises the significance of the food being eaten, such that a meal warrants sheva berachot even in the absence of panim chadashot,[11] [12] and even snacking (achilat ara’i) is forbidden on Shabbat if ma’aser had not been taken from the food.[13]
In truth, the question regarding wearing shorts on Shabbat pertains not only to the time of davening, but also throughout the day, and the issue applies even if one prefers the comfort of less formal clothing. The mandate to wear nice clothing on Shabbat[14] is not a matter of oneg (enjoyment), which lends itself to being influenced by personal preferences, but rather of kavod (honoring Shabbat).[15] In this regard as well, societal factors are crucial in determining what types of clothes are proper. For example, the Bi’ur Halacha[16] discusses whether wearing white clothes is considered being showy. In some circles, the same question could be raised about wearing a black hat, while in others a hat or even a shtreimel is expected. Factors such as age, weather, and venue (vacation resort, camp) may also play a role.
Logic dictates that since we are taking a practical, subjective approach, one should combine factors in order to see what is considered normal for a given time and place. On average, people dress more formally at tefilla on Shabbat than they do either at tefilla during the week or on Shabbat outside of shul. The same observation is true regarding how one dresses when appearing before important people, which is the model for attire for davening. One is likely to dress more formally in a formal setting in the presence of an important person than at a casual setting with the same important person in attendance. It follows, therefore, that the standard for clothes one wears during davening on Shabbat may be higher than what is usual for either weekday davening or leisure time on Shabbat.[17]
In summation, if it is rare for people to come to shul in your community with short pants on Shabbat, we would certainly agree with what the person who spoke to you said. (Hopefully, he said it in an appropriate way, which is not always easy to do.) If it is not rare but also not common to wear shorts in shul on Shabbat in your community, one needs to know where to draw the line. A local rabbi with a finger on the pulse of the community can do a better job of determining that than we can. In general, however, it is appropriate for the norm to be to wear long pants in shul on Shabbat.