How can it be that these Gedolei ha'Dor exempted themselves from the Sukah
in order to take care of their animals? We find several alternative
explanations in the Acharonim.
(a) The SEFAS EMES and others explain that these Gedolei ha'Dor were not
away from the Sukah the entire festival like Rashi says. Rather, they left
momentarily to check on their animals out in the fields. The Gemara (26a)
says that watchmen are exempt from the Sukah while they are working, and the
same applies to those guarding flocks of animals. Since these Gedolei ha'Dor
became momentarily exempt from the Mitzvah of Sukah, there was a Hefsek, an
interruption, from the Berachah which they recited at the beginning of the
festival, and thus their original Berachah will no longer apply when they
return to their Sukah. Therefore, they should have had to recite a new
Berachah if they did not hold like Rebbi Yochanan.
(b) The ARUCH LA'NER (in BIKUREI YAKOV 640:24) says that they went out to
learn Torah in isolation, for in such a manner they were able to achieve
great levels of holiness (see Zohar, Parshas Tetzaveh). Since they were
totally involved in a Mitzvah, they were Patur from the Sukah (25a, 26a).
(He adds that they returned to the city on Shemini Atzeres because they did
not want Hashem to hold back the rains on account of their being out in the
fields and exposed to the elements.)
(c) RAV REUVEN MARGOLIOS (in NEFESH CHAYAH 640:8) suggests that they did go
out specifically to watch their animals, but rather they were forced to flee
from the authorities, because it was a time of persecution against the Jews
in Pumbedisa (the city of Rav Huna bar Bizna).
(d) The YOSEF DA'AS cites RAV TZVI PESACH FRANK (in HAR TZVI) who writes in
the name of RAV CHAIM BERLIN (see also HA'OROS B'MASECHES SUKAH) that the
Gemara should read "m'Ifra Asu" instead of "m'Efer Asu." "Ifra" refers to
"Ifra Hormiz," the mother of Shevor, the king of Persia (Bava Basra 10b).
The Gedolei ha'Dor were involved in negotiating with the king on behalf of
the Jewish people, and therefore they were exempt from the Mitzvah of Sukah.
(e) The OR SAME'ACH (Hilchos Sukah 6:13) proposes a brilliant explanation
for this Gemara. The Gemara in Pesachim (52a) states that although it is
necessary to observe two days of Yom Tov in places where the people are not
expert in determining the new month (such as in Chutz la'Aretz), Talmidei
Chachamim who know how to calculate the new month may observe only one day
when they are in isolated, uninhabited areas (even in Chutz la'Aretz).
When the Gedolei ha'Dor went out to the fields in order to watch their
animals, they certainly dwelled in a Sukah. However, since they were out in
an uninhabited area, they were not bound to observe two days of Yom Tov out
of doubt (since they were all Talmidei Chachamim who knew how to calculate
the new month). Therefore, on the first day of Sukos they recited the
Berachah of sitting in the Sukah, and that exempted them from reciting the
Berachah the rest of the days (since they held like that opinion on 45b).
However, when they returned to the city on the eighth day, they were obliged
to sit in the Sukah, because they had to conduct themselves like the rest of
the people of Chutz la'Aretz (and treat the eighth day as a Safek, perhaps
it was really the seventh day). However, the Berachah which they had recited
on the first day could not cover the eighth day, because when they recited
the Berachah, they recited it on a *seven day* Sukos, and not on the eighth
day. Therefore, they would have had to recite a new Berachah upon sitting in
the Sukah on the eighth day. The fact that they did not recite a new
Berachah when sitting in the Sukah on the eighth day showed that they ruled
like Rebbi Yochanan!