Question: Can one fulfill one’s obligation to eat Seuda Shelishit (the third Shabbat meal) by eating cakes and fruit?
Answer: The Gemara (Shabbat 118b) states: “One must eat three meals on Shabbat.” This is derived from verses in the Torah regarding the Jewish nation’s sojourn in the desert, they did not have actual bread and their sustenance was the Manna that fell from Heaven. The verse (Shemot 16) states that Moshe told them: “Eat it ‘today’, for it is a Shabbat ‘today’ for Hashem; ‘today’ you shall not find it in the field.” From the fact that the verse uses the word “today” three times, our Sages derived that one must eat three meals on Shabbat. All three meals must be established on bread based on the words of the Rambam we have quoted in the previous Halacha that one must partake of bread during all three of the Shabbat meals.
The Samag and Tosafot (Shabbat 117b) rule in accordance with the opinion of the Rambam that one must partake of bread during all three meals, for our Sages derived the obligation to eat three meals on Shabbat from the verse regarding the Manna, which was the sustenance of the Jewish nation in the desert and which was, in fact, their bread. The Rosh, Ritba, Nimukei Yosef, Meiri, and other great Poskim rule likewise.
Nevertheless, Rabbeinu David Abudirhem (page 49d) quotes Rabbeinu Tam as writing that there is a distinction between Seuda Shelishit and the other meals in that one need not recite Kiddush before it and it is the conclusion of all of the Shabbat meals. Thus, one may fulfill one’s obligation of Seuda Shelishit by eating cakes or other pastries made out of the five types of grain. He proceeds to support this view. Maran Rabbeinu Ovadia Yosef zt”l (in his Chazon Ovadia-Shabbat, Part 2, page 343) quotes a question sent to Rabbeinu Tam from Rabbeinu Moshe of Fontaiza recorded in Rabbeinu Tam’s Sefer Ha’Yashar where Rabbeinu Tam proves from the words of our Sages that one may fulfill one’s obligation of Seuda Shelishit even by eating fruits; Rabbeinu Moshe mentions in the text of his question that he had heard Rabbeinu Tam instructing his followers that one may fulfill Seuda Shelishit by eating fruits. Indeed, Rabbeinu Tam replied that one may, in fact, fulfill one’s obligation by eating fruits and he proceeds to explain this issue eloquently.
Halachically speaking, Maran Ha’Shulchan Aruch (Chapter 291, Section 5) rules, as follows: “One must partake of bread for Seuda Shelishit. Some say that one may even use pastries made out of the five grains for Seuda Shelishit. Some say that one may even use things that are eaten together with bread, such as meat or fish. Some say that one may even use fruits for Seuda Shelishit. The first opinion that one must eat bread for Seuda Shelishit is the primary one unless one is overly full.”
This is indeed the correct Halacha and preferably, one should partake of bread during Seuda Shelishit. This is especially true regarding Shabbatot during the summer months (when the day is long) when there is no real reason to abstain from eating bread during Seuda Shelishit, for several hours have passed since the Shabbat day meal. On the contrary, one should be wise and not overeat during the day so that one will be able to partake of Seuda Shelishit in the most halachically preferable manner. Only if one is overly full and cannot eat bread during Seuda Shelishit may one fulfill Seuda Shelishit by eating a Kezayit of cake or other cooked foods made from the five grains. If one cannot eat cake, one should eat meat or fish. If cannot eat any of the above foods, one may even fulfill Seuda Shelishit by eating fruits.