Q) What is the latest time one can have se’udoh shlishis when Yom Tov falls on Motzo’ei Shabbos?
A) The Shulchan Aruch (OC 249:2) rules that it is forbidden to partake of a se’udoh on Erev Shabbos (see footnote[1] for the exceptions to this). However, this specifically refers to a type of meal that one is not accustomed to having on a weekday. The reason given is that one should be able to eat the Shabbos se’udoh with an appetite. This prohibition applies the entire day.
The Shulchan Aruch continues and says that it is permitted to eat and drink outside the framework of a se’udoh the entire Erev Shabbos. It is also permitted to partake of a regular meal that one is accustomed to eating on a weekday. The Shulchan Aruch adds that there is a mitzvoh to refrain from partaking of a se’udoh that one is accustomed to eating[2] on a weekday, from nine relative hours of the day. [The Mishna Berura (s.k. 17) explains that this works out to be the last quarter of the day.] There is no mitzvoh to refrain from eating and drinking outside of a meal[3].
The Pri Megadim writes that this also applies to Erev Yom Tov – since there is a mitzvoh to honour Yom Tov.
The Bi’ur Halocho (d.h. “milikvo’ah se’udoh”) defines “partaking of a meal” as eating an amount of bread that one is accustomed to, which causes satiation. However, eating a small amount of bread in order to relieve one’s hunger is not an issue. [The Bi’ur Halocho does not define clearly how much bread this is.]
In Siman 291, while discussing se’udoh shlishis on a Shabbos that is Erev Yom Tov, the Mishna Berura (s.k. 17) tells us that if one is able to eat a small se’udoh shlishis after Mincha, it is better to do so than to divide the morning se’udoh into two[4]. In Bi’ur Halocho (d.h. “achar sheyispalel”) the Mishna Berura explains that although the Magen Avraham writes that one should eat se’udoh shlishis [on Shabbos Erev Yom Tov] before sho’oh asiris; the Mishna Berura himself argues and maintains that the prohibition is only to begin a proper meal; however, to eat an amount of bread equivalent to slightly more than a k’beitzah is permitted even when Erev Yom Tov is a weekday [and all the more so when Erev Yom Tov is Shabbos].
The Remo in Hilchos Yom Tov (OC Siman 529:1) says that it is forbidden to eat from “the time of mincha” on Erev Yom Tov, just like it is forbidden on Erev Shabbos. The Mishna Berura (s.k. 5 and Bi’ur Halocho d.h. “mimincho”) says that the wording of the Remo is inaccurate; it is not actually “forbidden” rather “better to refrain”, and the time from which it is better to refrain is not the time of mincha ketana as the Remo mentions; rather half an hour earlier [i.e. sho’oh asiris].
In summary; when Yom Tov falls on Motzo’ei Shabbos it is better to refrain from partaking of a “full” se’udoh shlishis from sho’oh asiris. One should either eat a regular se’udoh shlishis before sho’oh asiris or eat a smaller amount of bread (i.e. slightly more than a k’beitzah) after sho’oh asiris.
[1] לפי הרמ”א (שם) סעודה שזמנה בע”ש כגון ברית מילה או פדיון הבן מותר
[2] ע’ ביה”ל ד”ה מלקבוע סעודה שלאכול מעט פת [שאינו רגיל בה בחול] אינו בכלל קביעות סעודה לענין זה
[3] מ”ב ס”ק ט”ו בלי קביעת סעודה מותר כל היום ואפ’ מצוה למנוע ג”כ ליכא
[4] היינו לברך ברכהמ”ז, ושוב ליטול ידיים ולברך המוציא