WHO IS YOTZEI THROUGH KIDUSH IN SYNAGOGUE?
(Rav): People who 'make' Kidush (listen to the Shali'ach Tzibur and have intent to be Yotzei) in synagogue are Yotzei Kidush [even if they did not taste the wine], but they are not Yotzei [the Berachah on] wine (even if they drank wine, once they leave the synagogue to go home they lose the Berachah, and must bless Borei Peri ha'Gafen on wine they will drink at home);
(Shmuel): They are not even Yotzei Kidush.
Question: According to Rav, why do they make Kidush at home?
Answer: This is for the sake of their households [which were not in synagogue].
Question: According to Shmuel, why do we make Kidush in synagogue?
Answer: Visitors who eat, drink and sleep in the synagogue are Yotzei through it.
This is like Shmuel taught elsewhere, that Kidush must be in the place where one eats (therefore, only the visitors who eat in synagogue are Yotzei).
Assumption: He disallows Kidush in one house and the meal in another house - but within one house, they need not be in the same place.
Rejection (Rav Anan bar Tachlifa): Often I saw Shmuel descend from the roof to the ground floor [and make Kidush again, when his Ner extinguished before he ate - Tosfos Rid; Tzelach - even though Kidush with intent to eat elsewhere in the house works, e.g. for visitors in synagogue, this is only b'Di'eved - therefore, he would descend before making Kidush, and not rely on intent to eat below].
Also Rav Huna holds that Kidush must be in the place where one eats:
Once, Rav Huna made Kidush and his lamp fell and extinguished [before he ate] - he brought his Kelim to the house where they were celebrating the wedding of his son, where there was light; he made Kidush and ate a bit there.
This shows that he requires Kidush to be where one eats.
Also Rabah holds that Kidush must be in the place where one eats:
Abaye: In Rabah's house, when he was Mekadesh he told us to taste a bit, lest the lamp go out where we were lodging [and we will not eat there], and we are not Yotzei with his Kidush [without eating], for Kidush must be in the place where one eats.
Question: Abaye taught that wherever Rav and Shmuel argue, Rabah always followed Rav, except for three Halachos in which he followed Shmuel:
One may remove Tzitzis from a garment to attach them to another garment, one may light a Ner Chanukah from another Ner Chanukah, and the Halachah follows R. Shimon regarding dragging:
(Beraisa - R. Shimon): One may drag a bed, chair or bench [on a dirt floor], as long as he does not intend to make a furrow.
Answer: Rabah followed the stringencies of Rav [with only three exceptions], but there are many leniencies of Rav he did not follow.
WHICH CHANGES MANDATE A NEW BLESSING?
(R. Yochanan): People who make Kidush in synagogue are Yotzei [Kidush and] even [the blessing on] wine.
This is like he taught elsewhere:
(R. Yochanan): The same law applies to a change of wine or place - one need not make a new blessing. (One does not say Borei Peri ha'Gafen again, but he says ha'Tov veha'Metiv if the new wine is better (Rashbam; Tosfos - or slightly worse).)
Question (Beraisa): A change of place mandates a new blessing; a change of wine does not.
R. Yochanan is refuted.
(Rav Chisda citing Rav Huna): A change of place from one house to another mandates a new blessing - but within one house it does not.
Support (Rav Idi bar Avin): A Beraisa was taught in the house of [or by] Rav Hinak like this!
Question: Does Rav Huna teach [in his own name] the same Chidush as a Beraisa?
Answer: [Yes -] he had not heard the Beraisa.
(Rav Chisda): A change of place mandates a new blessing only regarding foods that do not require a Berachah [after eating them] in their place (where they were eaten, e.g. bread; some include the five grains or all seven species of Eretz Yisrael);
No new blessing is required for foods that require a Berachah in their place.
Question: What is the reason?
Answer: Since he must return [to where he ate], it is considered a continuation of his meal.
(Rav Sheshes): A new blessing is required in either case.
Question (against Rav Chisda - Beraisa): If friends were reclining to drink and uprooted themselves to greet a groom or bride, they need not bless before leaving or when returning;
This is when an old or sick person remained there - if not, they require a Berachah Acharonah on what they ate, and a new Berachah Rishonah when they return.
'Uprooted' connotes that [normally, they would not leave suddenly without blessing, i.e.] they were eating foods that require a Berachah in their place - nevertheless, they must bless before leaving and when returning unless one of them remained!