1) HALACHAH: EATING ON EREV SHABBOS OR ON EREV PESACH
OPINIONS: The Mishnah (99b) states that one may not eat on Erev Pesach "close to Minchah time." The Gemara later (107b) explains that this refers to the ninth hour of the day. The Gemara here discusses whether or not a person is allowed to begin a meal after the ninth hour on Erev Pesach or on Erev Shabbos. It asks further whether or not one must stop a meal that he started after the ninth hour. These Halachos are the subject of a dispute between Rebbi Yehudah and Rebbi Yosi. (See Chart.)
What is the Halachah?
(a) TOSFOS and the RASHBAM (DH Amar Lo) explain that the Gemara concludes in accordance with Rav Huna's interpretation of the Mishnah. Rav Huna (99b) states that Rebbi Yosi -- who says that on Erev Shabbos one may start a meal up until nightfall -- agrees that on Erev Pesach, one may not begin to eat after the ninth hour. Since both Rebbi Yehudah and Rebbi Yosi agree that one may not begin a meal on Erev Pesach after the ninth hour, the Halachah follows their opinion.
With regard to Shabbos, the Halachah is in accordance with Rebbi Yosi who says that one is permitted to begin a meal after the ninth hour. The Halachah follows Rebbi Yosi whenever he argues with one of his colleagues (Eruvin 46b), and because the Halachah follows the opinion of the anonymous Mishnah, which Rav Huna attributes to Rebbi Yosi (and the Mishnah implies that only on Erev Pesach one must refrain from eating, but not on Erev Shabbos).
Regardless of when one began his meal, the Gemara says that on Shabbos one does not have to stop (like Rebbi Yosi). However, Shmuel was stringent and required one to be "Pores Mapah" (spread a cloth over the meal) and recite Kidush (but not to end the actual meal and recite Birkas ha'Mazon). With regard to Erev Pesach, the Halachah follows Rebbi Yehudah's opinion, that one must conclude his meal completely, as the Gemara says in the name of Rebbi Yochanan (or Rebbi Yosi bar Chanina).
(b) The ROSH, however, suggests that there is room to be more lenient on Erev Pesach when one has already begun to eat. He asserts that there is no reason to rule like Rav Huna (who says that Rebbi Yosi agrees with Rebbi Yehudah that one may not begin to eat after the ninth hour on Erev Pesach). Although when the Gemara discusses Rav Huna's explanation of the Mishnah it seems to reject the opinion of Rav Papa (who says that the Mishnah follows the view of Rebbi Yehudah, that one may not eat from the ninth hour on Erev Pesach, nor from nine and a half hours on Erev Shabbos), nevertheless there remains significant reason to accept the explanation of Rav Papa.
The Gemara rejects Rav Papa's explanation only because of a Beraisa in which Rebbi Yehudah states that one is forbidden to eat on Erev Shabbos from the ninth hour. This contradicts Rav Papa, who says that Rebbi Yehudah prohibits eating only from nine and a half hours. However, while that Beraisa contradicts Rav Papa, another statement supports Rav Papa -- "Halachah k'Rebbi Yehudah b'Erev Pesach." The simple understanding of that statement implies that Rebbi Yosi argues with Rebbi Yehudah even with regard to Erev Pesach. The Gemara, in an attempt to answer Rav Huna, is forced to interpret that statement as a reference to stopping a meal on Erev Pesach. According to Rav Papa, however, the statement is understood in its simple meaning.
Even though a Beraisa contradicts Rav Papa, perhaps it was recorded in error (as the Gemara itself suggests at the beginning of this Daf). If the Halachah is like Rav Papa, then Rebbi Yosi argues with Rebbi Yehudah even with regard to when one may start a meal on Erev Pesach.
The Rosh adds that, logically, there is more reason to differentiate between beginning a meal on Erev Pesach and beginning a meal on Erev Shabbos, than to differentiate between stopping one's meal on Erev Pesach and stopping on Erev Shabbos. On Erev Pesach, one must eat Matzah at night with an appetite. Therefore, one should not begin a meal close to the onset of Pesach. In contrast, the reason one must stop his meal at sundown is to honor the holiday with the recitation of Kidush. Both Erev Pesach and Erev Shabbos are the same in that respect (perhaps the honor of the Shabbos is even more important than Pesach). For these reasons, the Rosh concludes that the Halachah follows the view of Rav Papa.
Therefore, on Erev Shabbos, one is permitted to begin a meal all day, and when Shabbos arrives he does not need to stop (as Tosfos and the Rashbam rule, according to Rebbi Yosi). On Erev Pesach, the Rosh agrees that one may not begin to eat after the ninth hour, but not because that is the opinion of Rebbi Yosi (as Tosfos and the Rashbam write). Rather, it is because this is the opinion of Rebbi Yehudah, and the Gemara says that the Halachah follows Rebbi Yehudah with regard to beginning a meal on Erev Pesach.
However, when it comes to stopping one's meal, the Halachah follows Rebbi Yosi both on Erev Shabbos and on Erev Pesach. Accordingly, it suffices to be "Pores Mapah" and recite Kidush without beginning a new meal. The Rosh learns that when the Gemara says that the Halachah follows Rebbi Yehudah with regard to Erev Pesach, it refers only to when one may begin a meal, but not to when one must stop a meal.
(c) TOSFOS (DH Ein Mafsikin) quotes the BEHAG who modifies Tosfos' ruling with a stringency, with regard to beginning a meal on Erev Shabbos. The Behag rules that on Erev Shabbos, one is prohibited to eat from nine hours, even according to Rebbi Yosi. He suggests that Rebbi Yosi permits one to eat at that time only b'Di'eved (that is, if one started after nine hours, he does not have to stop), but, l'Chatchilah, he agrees that one may not start.
It is clear from the Gemara (100b) that Rebbi Yosi even permits one to begin to eat on Erev Shabbos after nine hours (see Rashbam there, DH Kan l'Achar Tesha). How can the Behag propose otherwise?
The VILNA GA'ON (OC 249:7 and 529:4) explains that since Rebbi Yosi states that "one does not need to stop his meal if he already started to eat," it must follow that one should not start to eat l'Chatchilah. How does the Vilna Ga'on understand the Gemara that says that Rebbi Yosi admits that one may start to eat l'Chatchilah? The Vilna Ga'on explains that there are two different meals under discussion. When the Behag says that Rebbi Yosi maintains that one may not begin a meal, he means that one is not permitted to begin the type of meal which one normally eats during the week, a large meal. The Gemara that says that one may begin to eat refers to a small meal.
This indeed is the way the RAMBAM rules in Hilchos Shabbos (30:4) and in Hilchos Yom Tov (6:16).
HALACHAH: The Halachah seems to be in accordance with both the leniency of the Rosh (b) on Erev Pesach, and the stringency of the Behag and Rambam (c) on Erev Shabbos.
The SHULCHAN ARUCH (OC 249:2) rules like the Rambam that a person should not begin to eat a regular meal (the type of meal he eats during the week) after the ninth hour on Erev Shabbos. On Erev Pesach, of course, one may not begin any type of meal after the ninth hour.
Included in this prohibition is one who begins to eat before the ninth hour with intent to continue until after the ninth hour (RASHBAM 107b, DH Sof Sof). One who intends to continue to eat after the time at which eating becomes prohibited is comparable to one who starts a meal at that time.
If one was in the middle of a meal on Erev Pesach when nightfall arrived, the SHULCHAN ARUCH (OC 472:3) rules that he is not required to stop with Akiras Shulchan (removal of the table and recitation of Birkas ha'Mazon). Rather, he merely needs to be "Pores Mapah" and recite Kidush. That is, the Shulchan Aruch seems to follow the ruling of the ROSH, that on Erev Pesach one need not stop immediately and recite Birkas ha'Mazon (as Rebbi Yehudah rules). (This may apply only if the meal was begun b'Heter, before the ninth hour. See Chart.)