Eiruvin 7:10-11

Eiruvin 7:10

According to Rabbi Eliezer, an eiruv and a shittuf may be made using any foodstuffs except for water and salt; Rabbi Yehoshua says that one must use a whole loaf of bread. It can be tiny but it must be whole; if it is broken, it may not be used.

Eiruvin 7:11

Rabbi Eliezer says that if a shopkeeper or a baker are among the residents of an alley, a person may give them money to acquire food for the eiruv on his behalf. The Sages say that this is an ineffective acquisition because the buyer never takes possession of his purchase. They agree that it is an effective acquisition if one gives money to a different resident (who is not a shopkeeper or a baker) because one may make an eiruv for another person based only on his consent. Rabbi Yehuda says that this only applies to eiruvei techumin (used to shift one’s Shabbos boundary) but that eiruvei chatzeiros (used to combine the residents of a courtyard) may be made for someone with or without his consent. One person may benefit another in his absence but he may not act to the other’s detriment in his absence. (Eiruvei chatzeiros are a pure benefit because they enable one to carry in the courtyard with no down side. Eiruvei techumin have a detriment in that whatever one gains in one direction, one loses in the opposite direction. Since a person might not agree to this, eiruvei techumin require consent.)