1) A BREACH IN THE FRONT OF A MAVOY
QUESTIONS: Rav Huna brei d'Rav Yehoshua says that when there is a breach four Tefachim wide in the front corner of a Mavoy, a Lechi or Korah cannot permit carrying in the Mavoy. Even though a breach in the side of a Mavoy is considered a doorway even when the breach is up to ten Amos wide, a breach in the corner cannot be classified as a doorway, because one does not normally build doorways in corners.
(a) Why does a breach in the corner invalidate the Lechi or Korah of the Mavoy only when it is four Tefachim wide? Even if it is less than four Tefachim wide (but more than three Tefachim; any breach less than three Tefachim is automatically mended by the concept of Lavud), it is not a doorway and it should invalidate the Lechi or Korah of the Mavoy!
(b) Moreover, the Gemara itself teaches that a breach between three and four Tefachim wide invalidates the Lechi or Korah of the Mavoy. The Gemara earlier (5a) says that the Amora'im agree with the ruling of Rav Ami and Rav Asi, who taught that even a three-Tefach breach invalidates a Mavoy if the solid wall between the entrance to the Mavoy (where the Korah rests) and the breach is less than four Tefachim. When the breach is in the front corner of the Mavoy, as in the case of the Gemara here, there obviously are not four Tefachim of wall from the Mavoy's entrance to the breach (since there is a breach there instead). Consequently, a breach of three Tefachim in the corner should invalidate the Mavoy!
(a) The RASHBA explains that the reason why a breach in the corner must be four Tefachim in order to invalidate the Mavoy is because only a "Makom Chashuv," a significant area, can invalidate a Mavoy. It is not enough to have a small breach. Only a breach of a significant size -- at least four Tefachim -- can invalidate a Mavoy.
(b) Even though Rav Ami and Rav Asi taught that a breach of three Tefachim is enough to invalidate a Mavoy and a significant area is not necessary, the case of the Gemara here is not comparable to the case of Rav Ami and Rav Asi. There, the Korah rests on a small piece of wall that is less than four Tefachim long. This small piece of wall is separated from the rest of the Mavoy by the three-Tefach breach. In such a case, even a small breach is sufficient to break off the part of the Mavoy upon which the Korah rests from the rest of the Mavoy. In contrast, the Gemara here discusses a Mavoy that has a wall at its front that spans across half of the entrance (as Rashi explains). The Korah rests partly on that wall and partly on the other wall (on the other side of the entrance to the Mavoy). The wall that extends across the front of the Mavoy, upon which the Korah rests, is more than four Tefachim long. Therefore, even if the corner is breached, the wall is a valid wall, the entranceway remains a valid entranceway, and the Korah remains a valid Korah. (CHIDUSHEI HA'RAN and other Rishonim)
2) "MAVOY AKUM" -- A BENT MAVOY
SUMMARY: Rav and Shmuel argue about the status of a "Mavoy Akum," a bent Mavoy (a Mavoy shaped like an "L" that opens to a Reshus ha'Rabim at both ends). Rav says that it is considered a Mavoy Mefulash, a Mavoy that opens on two sides to a Reshus ha'Rabim. Shmuel says that it is considered a Mavoy Sasum, a Mavoy that opens on only one side to a Reshus ha'Rabim.
What are the ramifications of Rav's opinion that a Mavoy Akum is considered a Mavoy Mefulash, and what are the ramifications of Shmuel's opinion that a Mavoy Akum is considered a Mavoy Sasum?
(a) There are two ways to understand Rav's ruling that a Mavoy Akum is considered a Mavoy Mefulash:
1. According to RASHI, Rav means that the Mavoy must have a Lechi at both ends and a Tzuras ha'Pesach in the middle. If there are two bends in the Mavoy (that is, the Mavoy is shaped like a "U"), Rav requires a Tzuras ha'Pesach in each of the two bends (Rashi, 6b).
The logic behind this approach is that we view each leg of the Mavoy Akum as a separate Mavoy. Since each leg of the Mavoy ends in a Reshus ha'Rabim and leads to a Reshus ha'Rabim (eventually) at the other end (after the bend), each leg is considered an individual Mavoy Mefulash. When placed in the bend where one leg meets the other, the Tzuras ha'Pesach serves both stretches of the Mavoy (since it is at the end of both stretches, and it can be seen from either side).
2. TOSFOS (10b, DH Oseh) and the ROSH cite the RI, who suggests another explanation. According to Rav, a Mavoy Akum must have a Lechi at one end, and a Tzuras ha'Pesach at the other end, and nothing at all in the bend. (See also Tosfos here, DH Amar Rav.)
According to this approach, Rav's logic is that the Mavoy Akum is considered Mefulash because it is all one large Mavoy. We do not view each straight stretch as an individual Mavoy, for if we did the Mavoy would not be considered Mefulash (since there is no exit at the far end of each leg, but only a bend).
(b) Shmuel disagrees with Rav and maintains that a Mavoy Akum is not considered Mefulash; it is viewed as a "dead end" alley just like an ordinary Mavoy. It is clear that Shmuel considers the bend to be an end to each stretch of the Mavoy that meets at the bend. Consequently, each stretch is viewed as an individual Mavoy that is open on one end to a Reshus ha'Rabim and closed at the other end (at the bend). There are two ways to understand Shmuel's ruling:
1. In his first explanation, Rashi suggests that according to Shmuel, to permit one to carry in such a Mavoy only two Lechis are needed, one at each end that opens to a Reshus ha'Rabim. The logical basis for this ruling is obvious. Since each straight stretch is viewed as a separate Mavoy, when there is a bend in a Mavoy (it looks like an "L") we treat it like two Mavoys, and thus we may carry in each one by adding a Lechi to its entrance. Similarly, when there are two bends in the Mavoy (it looks like a "U"), two Lechis are necessary, one at each entrance to a Reshus ha'Rabim.
2. Rashi cites a second explanation in the name of his teachers. According to his teachers, the dispute between Rav and Shmuel involves what must be placed in the center of a Mavoy Akum, at the point where it bends. Shmuel maintains that there must be a Lechi not only at the two ends of the Mavoy that open into a Reshus ha'Rabim, but in its bend as well. If there is more than one bend, a Lechi is required in each of the bends.
The logical basis for this is that Shmuel maintains that a Mavoy Akum is not exactly a Mavoy Sasum, since its dead end is not really "dead" -- the Mavoy is accessible from that end as well. Therefore, the bend needs a Lechi as well (just like any entrance to a Mavoy). However, since the bend does not directly exit into a Reshus ha'Rabim, it is not considered Mefulash and does not need a Tzuras ha'Pesach.