Siman - Eruvin Daf 10
- How wide can a mavoi be according to Rebbe Yehuda?
Abaye brings a Baraisa that taught that if a mavoi entranceway is wider than ten amos, he must decrease the width, and Rebbe Yehudah says that he does not need to decrease its width. The Gemara inquires how wide does Rebbe Yehudah permit a mavoi entrance to be.
Rav Achai proposed in the presence of Rav Yosef that Rebbe Yehudah allows a mavoi entrance to be thirteen and a third amos wide, from a kal vachomer based on Rebbe Yehudah’s view regarding the boards enclosing wells (פסי ביראות). If in the case of pasei birayos, in which it is allowed to have פרוץ מרובה על העומד – the gaps larger than the walled portion, yet it is not allowed to have a gap more than thirteen and a third amos, then in the case of the mavoi, in which it is not permitted to have פרוץ מרובה על העומד, all the more so it should not be permitted to have a gap more than thirteen and a third amos.
The Gemara challenges this reasoning, saying that perhaps it was specifically in the case of pasei birayos, where we are lenient with פרוץ מרובה על העומד, that we don’t not allow another leniency of wide gaps, but in the case of the mavoi, Rebbe Yehudah would permit even wider gaps.
A second challenge is brought and the question of how wide Rebbe Yehudah permits the gap to be is left unresolved .
- How to narrow a mavoi entrance that is too wide
The Gemara asks how to narrow a mavoi entrance that is too wide.
Levi initially brings a Baraisa , but rejects it. He then says to construct a board that is ten tefachim high and four amos long and stand it along the length of the mavoi so that it extends from the midpoint of the entrance towards the back of the mavoi. This divides the front of the mavoi into two distinct mavois, each which has an entrance of no more than ten amos.
- Chazaka that people do not abandon large entranceways for smaller ones
Rav Yehudah says that if the mavoi entranceway is fifteen amos wide, מרחיק שתי אמות ועושה פס שלש אמות – one leaves a space of two amos near the side wall and constructs a board that is three amos wide. This effectively closes off the entranceway, leaving an opening of ten. Similarly, says Rashi, one could apply the same method to both sides of a twenty amos wide mavoi.
The Gemara asks why there is no concern that people might enter through the small entranceway that is formed in the two amah gap, which would invalidate the lechi or korah used in the main entrance. The Gemara answers, חזקה אין אדם מניח פתח גדול ונכנס בפתח קטן – It can be assumed that a person will not abandon a large entranceway and enter instead through a small entranceway. Therefore, the main entranceway retains its status as the mavoi entrance.
