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Eruvin 5

1) A BREACH IN THE WALL OF A MAVOY FOUR "TEFACHIM" FROM THE ENTRANCEWAY

QUESTION: A Mavoy (with a Lechi or Korah) which has a solid wall extending four Tefachim from the entranceway before there is a breach (up to ten Amos wide) in the wall, one may carry in the Mavoy. But if the Mavoy's wall extends *less* than four Tefachim before the breach, one may not. The reason for this, explains the Gemara, is because four Tefachim is the minimum length of a Mavoy.

RASHI (DH Matir) explains that if people start using the breach as the entrance to the Mavoy and stop using the regular entrance, consequently, the regular entrance will be used only to enter an area that is less than four Tefachim long (i.e. the part of the Mavoy before the breach). Therefore that entrance is not considered a valid entranceway. Since the opening there is no longer considered an entranceway, the Korah over it can no longer serve to permit carrying in the Mavoy.

Rashi's explanation is difficult to understand. Rashi should have said simply that the *Mavoy* to which the main entrance leads is invalid because its wall does not extend four Tefachim, and therefore the Korah is not placed on a valid *Mavoy*! It makes no difference whether Why did Rashi have to add that the Korah is not a valid Korah because the entranceway is not a valid *entranceway*, since people no longer use that entranceway? ANSWERS:

(a) The RITVA answers that Rashi's explanation is based on the Gemara's conclusion. This Mavoy once was a valid Mavoy, but was breached. The Gemara concludes that it is more difficult to invalidate a Mavoy once it was built properly than it is to invalidate it if it has not yet been built properly. Therefore, since this Mavoy was a valid Mavoy, it takes more to invalidate it than the fact that the Mavoy is no longer four Tefachim long. Rather, it is a combination of two problems. First, the original opening is no longer considered an *entranceway* because people are not using it. Second, the Korah is not a valid Korah on top of a Mavoy because the *Mavoy* does not open into an area more than four Tefachim long.

(b) Alternatively, Rashi may mean that we do not view the area in the Mavoy before the break as an entirely separate Mavoy. If we did, the Korah would not permit carrying in the Mavoy even if the break was *more* than four Tefachim away from the entrance, since it is on a different Mavoy. Rather, if the entrance above which the Mavoy is placed is not used to gain access to an area at least 4x4 Tefachim, it is not considered an *entranceway* of a Mavoy. The Mavoy is still considered a valid Mavoy; it is the doorway which has lost its status. (M. Kornfeld)

QUESTION: The Gemara says that it is possible to have two four-Tefach wide doors opening into the sides of a four-Tefach long Mavoy, in such a way that they open on the corners. RASHI explains that each door opens at an angle, covering three Tefachim of the length of the Mavoy's wall, and one Tefach of the end of the Mavoy (see diagram in Rashi).

TOSFOS asks the obvious question. The diagonal of a right triangle whose sides are three Tefachim and one Tefach long is less than four Tefachim (~3.16). How, then, can doors four Tefachim long open into a Mavoy which is only four Tefachim long?

ANSWER: Perhaps Rashi maintained that at least a Tefach must be left from the walls of the Mavoy in order for it to be considered a valid Mavoy (perhaps because the minimum width of a Korah is one Tefach, and thus the walls must have an area upon which to place the Korah). Therefore, the length of the doors have to be decreased by a small amount, and it will be impossible for the doors to be a full 4 Tefachim.

As for the whether the doors are actually have to be a full 4 Tefachim long, it could be that Rashi is following his opinion elsewhere. In Shabbos (85a, see Insights there), RASHI says that seeds draw nourishment from the ground up to 1 1/2 Tefachim away, and since one plant's nourishment must be kept away from the nourishment of another type of plant, they must therefore be three Tefachim away from each other. Rashi (85a, end of DH v'Ha Ika, see Tosfos 85b end of the page) explains that a distance of the diagonal of two Tefachim by one Tefach is a sufficient distance to separate two types of plants. Even though this distance is not 3 Tefachim, Rashi maintains that the Rabanan allowed the three Tefachim to be measured by measuring the length up and across (2 + 1). Similarly, Rashi maintains that the four Tefachim necessary for the doorway of our Sugya may be measured by adding the length up and across (3 + 1).

5b