Very quickly review the גמרא דף יט: בעא מיניה אביי מרבה (first wide line) until the next בעא מיניה אביי (sixth wide line)
Summary:
We learnt three approaches to explain what the inquiry of אביי whether one may reduce the size of the opening between the פסי ביראות by extending the דיומדין?
1. Rashi & the ח’ ר”ן – Adding פשוטין /middle panels is noticable that it was placed there to reduce the size of the gap which is not as clear by just extending the דיומדין.
2. The ריטב”א – Adding פשוטין /middle panels is more preferred than extending the דיומדין when the width of the enclosed space between the פסי ביראות are less than 20 Amos as the פשוטין will divide the gap in half making each gap smaller than 10 amos.
However when the width of the enclosed space between the פסי ביראות is more than 22 Amos extending the דיומדין is preferred as that will result in עמוד מרובה – more solid walls than gaps on each side.
The question of אביי is whether ר”מ required פשוטין as most times it is more beneficial as the width of the enclosed space between the פסי ביראות is usually less than 20 Amos
3. The ח’ מהר”ל – perhaps extending the דיומדין although it physically reduces the size of the gap is insufficient as the concept of פסי ביראות is four corners composed of an אמה for each panel with a maximum of 10 Amos gap in between.
How do we conclude lhalacha?
See last line of ריטב”א דף יט: “בעא מיניה
See רבינו חננאל (on side of the Gemara)
Bring a proof from רבינו חננאל according to which of the three explanations of אביי inquiry he is aligned with.
Learn the second “בעא מיניה אביי מרבה” (sixth wide line) until the third בעא מיניה אביי (middle of the Amud)
Questions:
What is the uncertainty of אביי?
Why does אביי have reason to believe ר’ יהודה would have a different position than ר’ מאיר in regards to this question?
There are three explanations in the Rishonim
1. Learn Rashi
2. Learn רשב”א
3. Learn רמב”ם ה’ שבת פרק יז הלכה כט and the ח’ ר”ן
Learn תוס’ “ואם
Bring a proof from תוס according to which of the three explanations of the first inquiry of אביי he is aligned with.
The Gemara quotes ר”י who says there is a difference in size of gaps between פסי ביראות (allowed 13 1/3 Amos) and מחיצות (allowed 10 Amos). This contradicts what ר”י said in the first Mishna that the fourth side of a mavui can have gap of 13 1/3 Amos?
Learn ריטב”א for an answer
Learn the third “בעא מיניה אביי מרבה” (middle of the Amud) until the fourth בעא מיניה אביי (nine lines from the bottom of the Amud)