Beitzah Daf 17 ביצה דַף 17

It was taught in a Baraisa: שבת שחל להיות בראש חדש או בחולו של מועד – If Shabbos falls on Rosh Chodesh or Chol Hamoed, in the evening, morning and afternoon מתפלל שבע – he davens the regular seven berachos ואומר מעין המאורע בעבודה – and recites יעלה ויבא that reflects the occasion (Rosh Chodesh and Chol Hamoed), in the berachah of avodah. And if he did not mention it, מחזירין אותו – we make him recite it again. Rebbe Eliezer disagrees and says: בהודאה – He mentions it in the berachah of thanksgiving. Rashi explains that according to Rebbe Eliezer, one inserts יעלה ויבא in Hodaah, just as על הניסים is inserted in that berachah on Chanukah and Purim. And for Mussaf, he begins and concludes the middle berachah with mention of Shabbos, ואומר קדושת היום באמצע – and mentions the kedushah of Rosh Chodesh, or Chol Hamoed, in the middle. Rabban Shimon ben Gamliel and Rebbe Yishmael bno shel Rebbe Yochanan ben Beroka say that whenever one is required to recite the seven berachos, kedushas hayom is mentioned in the middle berachah, just like it is done on Yom Tov. Rav Huna said the halachah does not follow their opinion.

The Gemara asks, מי שלא הניח עירובי תבשילין - if someone did not establish an eruvei tavshilin, הוא נאסר וקמחו נאסר – is he prohibited to bake for Shabbos and his flour is also prohibited, or perhaps his flour is not prohibited? The Gemara clarifies that the nafka minah is that if his flour is also prohibited, then he must transfer ownership of his flour to others in order for them to bake for him. The Mordechai explains that while it is generally forbidden to acquire ownership of a possession on Yom Tov, it is permitted where it is necessary to facilitate performance of a mitzvah, as in the case of someone acquiring a lulav on Succos. Here too, acquisition of the flour would be necessary in order to prepare someone’s Shabbos meals. The Gemara brings an explicit Baraisa that states that in such a case, he should transfer ownership of his flour to others so that they may bake or cook for him.

The Mishnah on Daf 15b stated regarding the eruvei tavshilin, אכלו או שאבד לא יבשל עליו בתחילה – If one ate it, or it was lost, before the preparations for Shabbos had been completed, one may not cook in reliance on it primarily for Shabbos. On our Daf, Abaye said: נקטינן – We hold the following tradition, התחיל בעיסתו ונאכל עירובו גומר – If one started to prepare his dough for Shabbos and his eruv was eaten before he finished baking his bread, he may finish baking.