daf bit: Eruvin 26

(Today's daf is 27.)

An eiruv for Shabbat depends on providing for a communal meal, e.g. food that all in the shared courtyard can eat. (They are not required to actually eat it; it just needs to be available.) The mishna says that all foods can be used for this purpose except for water and salt, because water and salt do not make a satisfying meal. If a man vowed to abstain from food, the mishna points out, he is allowed to consume water and salt.

What about food restrictions? An eiruv may be prepared for a Nazarite (one who has vowed to abstain from wine) using wine; though the Nazarite can't drink it, somebody else can. Similarly, an eiruv for an Israelite may be prepared with terumah (food that is dedicated to the kohanim, or priests), but Symmachus dissents and says only unconsecrated foods may be used. So, Symmachus aside, the rule seems to be that if any member of the affected community can eat it, that's good enough. (26b, bottom of page)

(Aside: I learned as a result of asking a related question that in Pittsburgh, there is a communal box of matzah, with synagogues rotating annually who has custody of it. If nobody eats it I think it gets replaced once a year.)