כאילו קדוש שרוי בתוך מעיו שנאמר (הושע יא, ט) בקרבך קדוש ולא אבוא בעיר לא קשיא הא דמצי לצעורי נפשיה הא דלא מצי לצעורי נפשיה
as though a sacred object is immersed in his bowels, which he may not damage, as it is stated: “The sacred is in your midst; and I will not come into the city” (Hosea 11:9). This statement indicates that it is prohibited to take a fast upon oneself. The Gemara answers: This is not difficult. This first ruling, that one who fasts is sacred, is referring to a case where he is able to distress himself without causing bodily harm. That second ruling, that one may not overly burden his body, deals with a situation when he is unable to distress himself while avoiding all harm, and he proceeds to fast nevertheless.
ר"ל אמר נקרא חסיד שנאמר (משלי יא, יז) גומל נפשו איש (חסיד) [צ"ל חסד] ועוכר שארו וגו' אמר רב ששת האי בר בי רב דיתיב בתעניתא ליכול כלבא לשירותיה
Reish Lakish said: One who fasts is called pious, as it is stated: “The pious man does good [gomel] to his own soul; but he who troubles his own flesh is cruel” (Proverbs 11:17). The verb gomel can also mean weaning, or abstaining from unnecessary pleasure. Accordingly, Reish Lakish derives from this verse that one who abstains from food is called pious. Similarly, Rav Sheshet said: This student of a Torah academy who sits in observance of a fast has let a dog eat his portion. Since his fast weakens him and prevents him from studying Torah, it is considered as though a dog ate his meal, as the student derived no benefit from it.
אמר רבי ירמיה בר אבא אין תענית צבור בבבל אלא תשעה באב בלבד (אמר) ר' ירמיה בר אבא אמר ריש לקיש אין תלמיד חכם רשאי לישב בתענית מפני שממעט במלאכת שמים:
Rav Yirmeya bar Abba said: There is no completely stringent communal fast in Babylonia, except for the Ninth of Av alone. All other fasts, even those which are fixed and routine for the community, are treated as individual fasts, with regard to both the customs of the fast itself and the halakhot of who is obligated to fast. Rav Yirmeya bar Abba said that Reish Lakish said: A Torah scholar is not permitted to sit in observance of a fast, due to the fact that his fasting reduces his strength for the heavenly service of Torah study and mitzvot.
אוכלין ושותין משחשיכה כו': אמר רבי זעירא אמר רב הונא יחיד שקיבל עליו תענית אפילו אכל ושתה כל הלילה למחר הוא מתפלל תפלת תענית לן בתעניתו אינו מתפלל של תענית
§ The mishna taught that during the first set of fasts they eat and drink from after dark, and begin fasting in the morning. Rabbi Zeira said that Rav Huna said: With regard to an individual who took a fast upon himself, even if he ate and drank the entire night, on the following day he prays in the Amida the prayer of a fast, which begins: Answer us on the day of our fast. If after completing his fast he slept in his fast, i.e., he continued fasting throughout the night, he does not pray the prayer of a fast the next morning.
אמר רב יוסף מאי קסבר רב הונא סבירא ליה אין מתענין לשעות או דלמא מתענין לשעות והמתענה לשעות אינו מתפלל תפלת תענית
Rav Yosef said: What does Rav Huna maintain in this regard? Does he hold that one does not fast for only a few hours, i.e., that fasts that do not last from daybreak until nightfall are not considered fasts at all, and therefore these extra hours of the night are not part of his fast, or perhaps he holds that one does fast for a few hours, but one who fasts for a few hours does not pray the prayer of a fast?
אמר ליה אביי לעולם קסבר רב הונא מתענין לשעות והמתענה לשעות מתפלל תפלת תענית ושאני הכא דאיכא שעות דליליא דלא קביל עליה מעיקרא
Abaye said to Rav Yosef: Actually, Rav Huna holds that one does fast for hours, and one who fasts for a few hours does pray the prayer of a fast. But it is different here, as there are hours of the night that he did not take upon himself at the outset. Since one must take an individual fast upon himself beforehand, if he merely continues his fast into the night, these extra hours are not part of his obligation, and therefore he does not add the special prayer for a fast, Aneinu, on the following morning.
מר עוקבא איקלע לגינזק בעו מיניה מתענין לשעות או אין מתענין לשעות לא הוה בידיה קנקנין של נכרים אסורין או מותרין לא הוה בידיה במה שימש משה כל שבעת ימי המלואים לא הוה בידיה
§ The Gemara relates: Mar Ukva happened to come to the city of Ginzak. The inhabitants of Ginzak, among other matters, asked him three questions to which he did not know the answer: First, does one fast for hours, or does one not fast for hours? Mar Ukva did not have an answer readily available. Second, are the clay jars belonging to gentiles, which have been used for storing wine, permanently prohibited, or can they be rendered permitted? He did not have an answer readily available. Thirdly, in what garments did Moses serve all seven days of inauguration, as the acting priest when Aaron and his sons were initiated into the priesthood? Once again, he did not have an answer readily available.
אזל ושאיל בי מדרשא אמרו ליה הלכתא מתענין לשעות ומתפללין תפלת תענית והלכתא קנקנין של נכרים לאחר שנים עשר חדש מותרין במה שימש משה כל ז' ימי המלואים בחלוק לבן רב כהנא מתני בחלוק לבן שאין לו אימרא
Mar Ukva went and asked these questions in the study hall. They said to him: The halakha is: One fasts for hours, and he even prays the prayer of a fast. And the halakha is that the jars belonging to gentiles are permitted after they have not been used at all for twelve months. Finally, in what garments did Moses serve all seven days of inauguration? He did not serve in his own clothes, nor in the regular priestly garments, but in a special white cloak. Rav Kahana taught: Moses served in a white cloak that does not have a hem.
אמר רב חסדא
Rav Ḥisda said: