1. The גמרא says that לוי came to בבל on the 11th of תשרי which he knew to have been declared as כיפּור יום in ארץ ישראל. He told the people there “רבה דמערבא ביומא דבבלאי תבשילא "בסים. After making this statement, the people asked him to make it official and he says he couldn’t because he never heard ב"ד say מקודש מקודש. See the שפת אמת here who asks that if he couldn’t convert the day into כיפּור יום anyway, why did he bother saying anything? The פּותח שער shares a fascinating possibility and explains that when it is permissible for someone to eat on כיפּור יום, he/she may only eat the bare minimum such as bread and water and not delicacies. לוי was therefore telling them that although I can’t stop you from eating, you shouldn’t be “fressing” today but rather only eating bread and water. This explains why לוי complained that תבשילא דבבלאי בסים . The problem was not that they were eating but that they were eating tasty foods.
2. The גמרא says that לוי could not testify since he didn’t hear ב"ד say מקודש מקודש. רש"י understands this to mean that even though he left after on day 30, in which case ב"ד must be מעבר the month, he still could not testify due to the תקנה. See the ריטב"א here who explains that part of the תקנה itself was that people who lived in faraway places would not be allowed to act on your knowledge and change dates of holidays if you hadn’t heard from the court itself, although you knew that ב"ד was מעבר the month. See the טורי אבן who explains that לוי could not testify since he was only an עד אחד, and an עד אחד is not believed against a רוב (most years אלול was not מעובר). However, the פּשטות of our סוגיא is not that way. See the נצי"ב בהעמק שאלה אות ז who says that an עד אחד would be believed here since it is a מילתא דעבידי לאגלויי. See the בעל המאור here who learns completely different from רש"י. He understands that לוי left during the middle of the month after hearing that ב"ד planned to be מעבר the month. As such, he could not give testimony since they may have changed their minds.
3. The גמרא says that when the בית המקדש stood, witnesses could be מחלל שבת to testify about the new moon every month מפּני תקנת הקרבן. The ראשונים understand this in different ways. תוספות ד"ה על שני understands that witnesses could be מחלל שבת to testify because ר"ח is also called a מועד. Based on that, it should have been מותר to be מחלל שבת to testify at all times in history, even without a בית המקדש. However, the חכמים felt they needed to forbid it. Nonetheless, in the times of the בית המקדש they kept the original היתר מן התורה due to תקנת הקרבן. See the רבינו חננאל here who says that the reason one can be מחלל שבת to testify about the new moon is since the קרבן מוסף of ר"ח is דוחה שבת, so the witnesses can be מחלל שבת in order that the קרבן מוסף be brought at the correct time. According to that, when there is no בית המקדש, the witnesses would be forbidden מדאוירייתא to be מחלל שבת to testify. In a similar vein, see the ן“הר חידושי who says that זכאי בן יוחנן רב was דקרא טעמא דורש and understood that the only reason the Torah would have allowed one to beמחלל שבת for ניסן and תשרי must have been for the קרבן or מועד תקנת. Therefore, there is no היתר even מדאורייתא if there is no המקדש בית on any month where there is no מועד. Based on this, he asks why did the Torah not allow the שלוחין be שבת מחלל for מועד תקנת? His answer is somewhat surprising: The Torah always goes with רוב, and since most Jews lived close enough to ירושלים to find out the correct day, the Torah wasn’t חושש for the others who lived very far away.
Learn It. Review It. Own It.