Eruvin 49 – How does the eruv really work?

If people from different houses share a common courtyard, this is similar to a street, so the Sages prohibited them to carry in the courtyard on Shabbat – unless they put some common food (eruv) in one of the houses, each one contributing his portion.

How does this device work? Shmuel says that everybody acquires a portion in this house where the eruv is stored. The courtyard then belongs to this one house, is a single area, and they can all carry there. We can ask Shmuel that if so, why do they need bread at all? Let them use the money! Shmuel will answer that money is not always available on Friday afternoon, but bread is.

However, Rabbah says that the eruv works because where your food is – that's where you live, and in effect, everybody temporarily moves into the house with the eruv. What difference does it make, and why do we need different explanations?

The first difference is when they made the eruv with baskets, not bread. It works according to Shmuel, because they acquire a portion in the house, but not according to Rabbah because a person does not live where his basket is.

The second difference manifests itself if they all put together pieces of bread, each worth less than a small coin, prutah. Now it will not work according to Shmuel, because a value less than a small coin can not acquire anything. However, one can establish his residence even with a small piece of bread, and so this justifies Rabbah.

Finally, the third difference is when they ask a minor to collect bread from everybody. Again, it does not work according to Shmuel, because a minor cannot be an agent to acquire things, but he can perfectly well carry bread to a house and deposit it there, just as Rabbah said.

Art: Pieter De Hooch - The Courtyard of a House in Delft