Siman - Eruvin Daf 76

• The בית שער ובית question

Rachavah tested the Rabbanon with the following question: If there are two chatzeiros with two houses between them, and one chatzeir placed its eruv in the house which adjoins the other chatzeir, and the other chatzeir did the same and placed its eruv in the house adjoining the other chatzeir, do they each acquire an eruv or not? The question hinges on the following: Do we judge each house as the house for an eruv on the far side, and the house in between as a בית שער – a gatehouse, or do we judge each house as a בית שער, to the chatzeir that adjoins it? The Rabbanon answered that either way they do not acquire an eruv. If each house is deemed a בית שער it does not work since an eruv in a בית שער is invalid. If each house is deemed a house, then each chatzeir would have to walk through a house that was not joined in its eruv.

The Gemara clarifies that this is different than bein hashemashos which can be deemed halachically nighttime for some and daytime for others, since לא מינכרא מילתא – it is not a noticeable thing, since the first part could be day and the latter part night. It is therefore not a clear contradiction, and people will take these halachos seriously. A house, however, must be either a house or a בית שער, not both. Rashi explains that to consider it as a house to one person and as a בית שער to another, will make this halacha look like a joke.

• A window between two chatzeiros

The opening Mishnah of the seventh perek states, חלון שבין שתי חצרות ארבעה על ארבעה בתוך עשרה – In a case of a window between two chatzeiros that is at least four tefachim by four tefachim in size and located within ten tefachim of the ground, מערבין שנים – the residents of the two chatzeiros may join in two independent eruvs, because they are still considered separate areas, ואם רצו מערבין אחד – or if they desire they may join in one communal eruv because the window connects them. Rashi explains that since the height of the wall to the window is less than the ten-tefachim minimum height of a mechitzah, and since the window’s size qualifies it as a portal, the two chatzeiros are considered connected and may join in an eruv.

Rebbe Yochanan said that a round window in the wall must have a circumference of twenty-four tefachim, and the lower two tefachim and a bit more must be within ten tefachim of the ground so that if one inscribes a four by four square inside the circle it will be found that part of the square is within ten tefachim of the ground. The Gemara analyzes this ruling.

• A window between two houses

Rav Nachman said, לא שנו אלא חלון שבין שתי חצרות – this ruling was only learned regarding a window between two chatzeiros, אבל חלון שבין שני בתים – but a window that is between two houses,  אפילו למעלה מעשרה נמי – even it is completely above ten tefachim, אם רצו מערבין אחד – if the residents of the two homes want to join in one mutual eruv, they may. The reason for this is, ביתא כמאן דמלי דמי – a house is regarded as being full of objects. Therefore, the window is considered as though it were not higher than ten tefachim from the floor.