- Following chumros when if they do not contradict
On Daf 6b we learned that there was a מבוי עקום– a bent mavoi in Nehardea, with three intersecting mavois in the shape of the letter “ח”. The residents followed the stringencies of both Rav and Shmuel. The Gemara asked how they could do so, for a Baraisa taught, מחומרי בית שמאי ומחומרי בית הלל – One who follows the stringencies of both Beis Shammai and Beis Hillel, עליו הכתוב אומר "הכסיל בחשך הולך" – regarding him it is said, “The fool goes in darkness”?
On our Daf, Rav Sheizvee explains that the Baraisa’s rule not to follow the stringencies of two authorities only applies, היכא דסתרי אהדדי – where they contradict each other. As an example, the Gemara brings a machlokes between Beis Shammai and Bais Hillel regarding how much of a spine or skull must be missing for them not to impart tumah in an ohel. Beis Shammai’s shiur is larger than Beis Hillel’s making him the more stringent opinion. When the same shiurim are applied to determining when an animal is considered a treifah, Beis Hillel’s smaller shiur makes him more stringent. So the chumrah and kulah regarding tumah results in the opposite position in the case of a treifah. This is what the Baraisa was referring to.
In the case of the mavoi akum in Nehardea, the stringencies did not contradict each other.
- When Rabbanon and Chananya disagreed
Rav Yehudah said in the name of Rav that when the Tanna Kamma and Chananyah argued regarding the adjustments of a mavoi mephulash, it was only when the mavoi opened on both ends into a reshus harabim Med’Oraysa, such as a סרטיא – a public thoroughfare,or a פלטיא – a public square , that Chananyah required a door at one end. But if the mavoi opened into a public thoroughfare at one end and a field (which is not Med’Oraysa) at the other end, or it opened into fields at both ends, then even Chananyah agrees that, עושה צורת הפתח מכאן ולחי וקורה מכאן – one constructs a tzuras hapesach at one opening and a lechi or korah at the other opening.
- Mavois that open into a backlot or a chatzeir
Rav Yosef said in the name of Rav Yehudah, if a mavoi opened into a reshus harabim at one end, אם היה כלה לרחבה -but at the other end it terminated into a back lot, which in turn opened into a reshus harabim, אין צריך כלום – it does not require any adjustment at all on the back lot side, but only a lechi or korah at the end where it opens directly into the reshus harabim, like any closed mavoi.
Abaye said to Rav Yosef that this ruling of Rav Yehudah reflects the ruling of Shmuel and not Rav, as it contradicts Rav in two ways. One seeming contradiction is that Rav rules that a מבוי שנפרץ במלואו לחצר – a mavoi that was breached along its entirety, leaving it completely open to a chatzeir, ונפרצה חצר כנגדו – and the far wall of the chatzeir was breached opposite the mavoi, opening the chatzeir to a reshus harabim, חצר מותרת ומבוי אסור – carrying in the chatzeir is permitted but carrying in the mavoi is prohibited, unless adjustments are made. The Gemara resolves this contradiction as well as the second one.
