I have noticed that people seem to be particular about sitting for saying Al Hamichya (or Birkas Me'ein Shalosh in general).
Is there halachic reason (source and 'svara') to sit for this bracha? If so, what is it?
The Shulchan Aruch 183:10 writes :
יֵשׁ אוֹמְרִים שֶׁגַּם בִּרְכַּת מֵעֵין שָׁלֹשׁ צָרִיךְ לְאָמְרָהּ מִיֹּשֶׁב (There are those who say that by birkas mein shalosh needs to be recited while seated).
The Mishna Brurah writes:
שגם ברכת מעין שלש - עיין בביאור הגר"א שתלה דין זה במה שמבואר לקמן בסימן קפ"ד ס"ג והרמב"ם שהוא בעל דעה זו אזיל לשיטתו שם ולפ"ז בחמשת מיני דגן עכ"פ לכ"ע צריך להיות דוקא ברכה אחרונה שלהם בישיבה:
I have been told that this is part of showing respect for the shulchan and the meal served on it, as well as showing that one is connecting the bracha acharonah to the actual food that has been eaten. The reasons often given connect this to the reasons that there is a minhag to sit for kiddush.
The Reasons to sit for kiddush. There are a number of sources that would indicate a preference for sitting during the recitation of kiddush:
A. Tosafot (Berachot 43a) states that in order to include others in your recitation of kiddush it is necessary for everybody to sit, as an indication that they are all joining together to discharge their obligation through the kiddush of one of them. Tosafot even wonders why we have the custom to stand for havdalah when we are motzi others. They therefore suggest that it is best to sit for havdalah as well. (Regarding sitting during havdalah see Rama 296:6, Biur Hagra ibid., and Ma’aseh Rav 103.)
B. The gemara Pesachim 101a records the comment of Shmuel that one must recite kiddush in the same place that he will have his meal. It is clear in the gemara that this requirement does not only involve reciting kiddush in the same house that one will have his meal, but even in the same room where the meal will take place. The Mishnah Berurah (271:46) cites poskim who suggest that one should also recite kiddush in the exact spot that he will have his meal. As such, one who will eat sitting down should recite kiddush while sitting down as well.
C. The gemara and rishonim do not openly discuss that issue of standing versus sitting for kiddush. In all likelihood, there was only one custom during those times in history, thereby obviating the need for any debate about this matter. The question though remains, what was the custom that everybody had accepted without any opposition voiced against it. The Rambam (Hilchot Succah 6:12) writes that on the first night of Succot one should recite kiddush while standing, because the beracha of leshev b’succah should be recited prior to performing the mitzvah (of sitting in the succah). The Ra’avad comments that he had never heard of such a custom. Additionally, he argues, even if the berachah is recited while seated, it will still precede the primary aspect of the mitzvah of succah, the eating in the succah. Magid Mishnah adds that the words “leshev b’succah” do not reflect an obligation to sit in the succah. Rather, it reflects an obligation to dwell in the succah. After all, one who spends his entire day in the succah, eating and drinking standing up has certainly fulfilled his obligation of yeshivat succah. Based on this discussion, it seems that all of these rshonim took for granted that normally kiddush was recited while sitting down. The only debate revolved around the first night of Succot because of factors that are unique to that holiday.
V. Conclusion. We have outlined the various considerations to be taken into account when deciding whether to sit or stand for kiddush. As a practical matter, most Chassidic poskim have followed the custom of the Arizal to stand, and the Rama sanctions this custom. However, some later poskim have pointed out that this ruling should not apply to Yom Tov or daytime kiddush where it is preferable to sit. Rav Hershel Schachter shlit”a once told me that even one who plans to change his family custom in favor of a custom that he believes to be more halachically viable, he should maintain the old custom when reciting kiddush in front of his parents.