Siman - Eruvin Daf 16

• שלש מדות במחיצות

On Daf 15b a machlokes is introduced regarding פרוץ כעומד - if the gaps in a partition equal the walled portion. Rav Pappa says it is mutar to carry in an area enclosed by such partitions, whereas Rav Huna brei d’Rav Yehoshua says it is forbidden.

As part of the Gemara’s analysis to determine who the halachah goes according to, in our Daf a Baraisa from Kilayim is brought that presents שלש מדות במחיצות - three categories of partitions that permit planting something next to another planting, which would be kilayim when planted next to each other without a partition:

- Whenever the solid sections are less than three tefachim, it is necessary that the gap in between the sections should not be three tefachim wide כדי שלא יזדקר הגדי בבת ראש – so that a kid goat cannot leap headlong through the partition, (which would cancel לבוד from working). The gap, though, can be wider than the solid portions.

- When the solid portions are between three and four tefachim, the gaps cannot be as wide as the sections themselves. And if the gaps are even wider than the solid portions, then it is prohibited to plant even opposite the walled portions.

- When the solid portions are between four tefachim and ten amos, the gap cannot be as wide as the solid portions. If it is, then it is permitted to plant opposite the solid portions but prohibited to plant opposite the gaps. Rashi explains that a walled section that is four tefachim wide is considered to be independently significant.

• Using ropes and poles to create a mechitzah

The next Mishnah states that a caravan may surround its encampment with three horizontal ropes one above the other, provided that there is not a gap between ropes of three tefachim for the purpose of lavud to take effect, and that the total thickness of the ropes is more than one tefach, so that the height of the mechitzah is at least ten tefachim. It is also permitted to surround the caravan with vertical poles provided that the gaps between poles do not exceed three tefachim, in order for lavud to take effect.

• Rebbe Yehuda’s position regarding an individual using ropes and poles

The Gemara notes a contradiction between Rebbe Yehuda In the Mishnah, who said that the inferior partitions of ropes and poles are only permitted for caravans but not for individuals, and a Baraisa where he says, רבי יהודה אומר כל מחיצות שבת לא התירו ליחיד יותר מבית סאתים – the Chachomim did not permit these inferior Shabbos partitions for individuals in an area that encloses more than two beis se’ah. This implies that these partitions are permitted to individuals if it is two beis se’ah.

The Gemara concludes that Rebbe Yehuda in the Mishnah was forbidding these partitions for individuals only if the enclosed area was greater than two beis se’ah.