Siman - Eruvin Daf 5
- The size of a mound under a korah
On Daf 4b, a machlokes was brought in a case where one wanted to lower a mavoi entrance that was above twenty amos, by building up the ground beneath the korah. Rav Yosef said that the mound must be at least one tefach wide extending into the mavoi, and Abaye said it must be at least four tefachim wide.
One explanation for the basis of the machlokes is as follows. Rav Yosef holds, מותר להשתמש תחת הקורה – it is permissible to carry directly under the korah, and therefore the person will notice the korah and be reminded not to carry in reshus harabim. Abaye disagrees and holds, אסור להשתמש תחת הקורה – it is forbidden to carry directly under the korah, and therefore the korah must be recognizable when one is not standing directly underneath it. Rashi explains that once the mound must extend past the korah, it is required to have a choshuv width, which is the width of four tefachim.
A second explanation of the machlokes is that everybody holds, מותר להשתמש תחת הקורה - it is permissible to carry under the korah. However, they dispute the purpose of the korah. Rav Yosef holds that it is there to serve as a heker, and therefore one tefach is sufficient. Abaye holds that it is there to serve as a mechitzah, and a mechitzah is only halachically considered a partition when it sets off an area that is at least four by four tefachim. The Gemara brings two additional explanations.
- What kind of mavoi is it permissible to carry in?
It was taught in a Baraisa, אין מבוי ניתר בלחי וקורה עד שיהו בתים וחצרות פתוחין לתוכו – Carrying in a mavoi is not permissible with a lechi or a korah unless there are courtyards and houses opening into it, meaning at least two courtyards with at least two homes in each courtyard.
Rav Nachman said, נקיטינן – We have the following tradition, איזהו מבוי שניתר בלחי וקורה – Which kind of mavoi is permissible to carry in with a lechi or a korah? כל שארכו יתר על רחבו ובתים וחצרות פתוחין לתוכו – Any mavoi whose length is greater than its width and that courtyards and houses open into it. Rashi explains that a square mavoi has the status of a chatzeir which has more extensive requirements to permit carrying within it.
- A lechi that is four amos wide
Rami bar Chama said in the name of Rav that if a lechi protrudes four amos into the entranceway, נידון משום מבוי – it is judged as a wall of the mavoi, וצריך לחי אחר להתירו – and it therefore requires another lechi to permit carrying into it.
• Rav Pappa says one should place the lechi on the other side of the entrance way where it will stand alone and will not be mistaken as part of the original wide lechi.
• Rav Huna the son of Rav Yehoshua says that one may even place it next to the wide lechi, if he makes it taller or shorter, or thicker or thinner, so that it is distinct.
