As mentioned in other posts, during Sukkos there is a commandment to sit in the Sukkah. Our Sages have written that sit means we should sit in the Sukkah as we would dwell in our homes.
Just as we eat in our homes, so too should we eat in the Sukkah. However, this rough guideline is just that. There are many laws concerning how we are to properly discharge the mitzvah (commandment) of sitting in the Sukkah. Some of these laws unfortunately are unknown, yet fundamental to the correct performance of the mitzvah of sitting in the sukkah.
As a preface it is important to know that not saying the bracha (blessing) before the performance of a mitzvah in no way hinders or obviates the fulfillment of that mitzvah. That is the reason that we make the bracha on the Lulav and Esrog (the Four Species – see vol I:47 ) with the Esrog upside down. One cannot fulfill the mitzvah of Lulav if any of the Four Species is upside down. The species must be held in the way that they grow in order to properly fulfill the commandment. By holding the esrog upside down before we recite the blessing, we ensure that the bracha is said first. If the mitzvah would not be done this way it is conceivable that one might take the Lulav and Esrog with the intention to fulfill the mitzvah and thereby lose the opportunity to make the bracha. (A bracha generally cannot be said after the fulfillment of a mitzvah – only before.)
Another factor to be known is that when there is a question, in law, as to the need to say a bracha (a blessing) one is not said. The Torah requires all males over thirteen years old to leave their permanent dwelling and take up a temporary dwelling for seven days beginning with the fifteenth day of the Jewish month of Tishrei. In the case of Sukkah, a biblical requirement prevents the eating of a minimum volume of certain foods outside the Sukkah. There is unanimity concerning some items but there are differing opinions concerning others.
The following are some of the practical rulings that result in making the recitation of the following blessing : Baruch Ata Ad-noi El-heinu Melech HaOlam Asher Kidishanu B’Mitzvosav V’Tzivanu Leishev baSukkah,” Blessed are you Hashem our G-d, King of the World, who has sanctified us with His commandments and commanded us to sit in the Sukkah:
Even if one is sleeping or doing other activities in the sukkah the bracha of “leishev baSukkah”(the blessing for sitting in the sukkah) is NOT said. It is only said before (or during) eating. [Shulchan Aruch (Code of Jewish Law) O.Ch. 639:8.]
For one to be permitted to say the bracha of “leishev baSukkah” a minimum of a kibeitza (the volume of an egg calculated by the displacement of water. This volume equals to double that of a kizayis; the volume of an olive) must be eaten in the sukkah. [O.Ch. 639:2]
The bracha of “leishev baSukkah” would therefore be is said only when one is eating a minimum of the above amount of bread.
This bracha would be said when one is eating a minimum of the above amount of non-bread products made from food of the five grains (wheat, barley, rye oats, spelt) according to Aruch HaShulchan 639:27.
According to Mishnah Brura 639:13,15-16 and Kaf HaChaim 639:33 the following applies for the five grains:
The bracha is said only if a) one establishes his meal on these items by eating an amount three or four times the normal kibeitza b) one normally eats a kibeitza or more of cake for breakfast (with coffee, etc.) c) on Shabbos (Sabbath) or Yomtov (holidays) when one may eat a kibeitza or more of cake after reciting the Kiddush on wine before the meal. (One would not make the blessing during the Chol HaMoed [intermediate] days even though the prevalent custom is to make the bracha. [See Aruch haShulchan above.] If one does make the bracha on a weekday then one should sit awhile in the sukkah after eating in order to do some other activity.)
One does not make the bracha of “leishev baSukkah” when making Havdalah (the blessing marking the separating of Shabbos and Yomtov from weekday) upon conclusion of the festival days. [O.Ch. 369:2 MB.#13.]
This in no way should be construed as limitations to the requirement of eating in the sukkah. That is a totally different discussion and in very many cases one would still be obligated to eat in the sukkah while being exempt from the bracha. As mentioned above, the recitation of the bracha does not affect performance of the mitzva. Rather, it is an added layer which carries with it its own set of laws. Being that we are to live in the Sukkah while the opportunity presents itself, any time in the Sukkah is time well spent. While according to most authorities, drinking coffee alone would not necessitate the recitation of the bracha on the Sukkah, it is still worthwhile and praiseworthy to drink the coffee in the Sukkah. Many of the great sages spent much time in the Sukkah. They ate, drank, slept, and studied in the Sukkah. We as well want to gain the most from the Sukkah experience, and that is why we are to spend time in the Sukkah.
Our desire to spend time in the Sukkah, however, may be challenged. Inclement weather is not particularly conducive to staying outdoors in a dwelling with holes in the roof. We are only commanded to live in the sukkah as we would in our homes. Would we stay in our homes if there was water dripping through the roof? This presents us with another issue: What do you do if it rains on the first night (or second night, in the Diaspora) of Sukkos (when we have a positive commandment to eat in the Sukkah)?
While it is not within the scope of this article to deal with all the philosophical implications of rain on Sukkos, suffice it to say that our sages have told us that it is not a sign of blessing to be forced out of the Sukkah. (See vol. II:20 ) We pray, therefore, that this question remains in the field of the theoretical.
To properly understand the following answer, a number of fundamental points must be prefaced.
To say Birkas haMazon (Grace After Meals, recited after any meal at which bread is consumed) at any time, a minimum of a kizayis (the volume of flour equal to the volume of an olive) must be eaten within approximately four minutes.
For one to be permitted to say the bracha of “leishev basukkah,” a minimum of a kibeitza (the volume equals to double that of a kizayis) of bread or cake must be eaten in the sukkah.
The bracha of “Shehechiyanu” (Who has renewed us and sustained us and brought us to this time, recited upon the first performance of each mitzva on the holiday) relates also to the Sukkah; but only on the first night of Sukkos.
There is disagreement as to the requirements of eating in the sukkah on the first two nights of Sukkos if it is raining. The opinion of the Rama is that there is a requirement to eat a minimum of a kizayis in the sukkah, even in the rain, on the first two nights. Others are of the opinion that the exemption of eating in the sukkah in the rain applies equally to all the days of Sukkos.
As we said above, the inability to make a bracha on a mitzvah does not affect the fulfillment of that mitzvah.
We are strict whenever we have a doubt concerning the fulfillment of a biblical law (such as eating in the Sukkah on the first night of Sukkos).
We do not make a bracha whenever we have a doubt concerning the correctness of that bracha.
On the first night of Sukkos a married man or one eating with female family members or young children should wait approximately one hour to see if the rain will stop. If the rain continues he should go into the Sukkah; say the Kiddush with the “Shehechiyanu” blessing, wash as one usually does before the consumption of bread and eat at least a kizayis of bread in the rain. He should not say the blessing of “leishev baSukkah.” He may then complete his meal in the house. After the meal, he should wait until slightly before the Halachik midnight to see if the rain will stop. If the rain stops, he then washes, enters the Sukkah again, says the brocho “leishev baSukkah,” eats at least a kibeitza of bread and then says Birkas haMazon.
On the second night, if it rains, one need not wait at all and he may begin his meal immediately in the house. Kiddush with “shehechiyanu” is made in the house. This would even apply to a single person. At the end of the meal, before saying the Grace After Meals, even if it is still raining, he should eat a kizayis of bread in the Sukkah in the rain. Again, a bracha of “leishev baSukkah” is not said. A bracha of “shehechiyanu” is not needed for the sukkah on the second night. One may then go back into the house to say the Grace After Meals. According to many opinons, even on the second night, one should wait again until slightly before the Halachik midnight to see if the rain stops. If the rain does stop then the procedure is the same as the first night. On all other days or nights of Sukkos, if the rain is so strong in the Sukkah that if it was raining in the house a person would be driven out of his home to find other shelter, or if the rain is ruining his food, preventing him from eating, he need not eat in the Sukkah. If one has already started his meal inside, and the rain stops, he may complete his meal in the house.
This d’var halacha courtesy of Torah.org