Arranging an eiruv tavshilin for other people

A person who prepared all of his Shabbos needs before Yom Tov does not need to make an eiruv tavshilin. One person may arrange an eiruv tavshilin on behalf of another person in a different household, but it is preferable for each householder to make his own. The primary purpose of the eiruv is to remind a person that although he may cook on Yom Tov for Shabbos, he may not cook on Yom Tov for another day. This reminder is best served when each person makes his own eiruv tavshilin. In addition, it is appropriate for a person to involve himself in mitzvos and not to rely on others to do them on his behalf.

[שו"ע תקכז, ז, משנ"ב כה, ושעה"צ לה ו־מ; ביאורים ומוספים דרשו, 35]

Arranging an eiruv for all the residents of the city

There is a mitzvah for the leader of every city to arrange an eiruv on behalf of all the townspeople. According to many Rishonim, anyone may rely on this eiruv. A minority opinion maintains that the eiruv can only be used by people who forgot to arrange, or lost, their own eiruv. According to this opinion, a person who relied on the community’s eiruv more than once may not continue to rely on it. Later poskim disagree about whether (according to this opinion) these multiple uses must be in succession. Shulchon Aruch rules according to this opinion. One may rely upon the lenient opinion for the sake of kavod Shabbos.

[שו"ע תקכז, ז, משנ"ב כב ו־כו, ושעה"צ לב ו־מ; ביאורים ומוספים דרשו, 29]

A person who will be making an eiruv on behalf of other people can arrange for a third party to acquire the eiruv on their behalf. The third party must be a person who has the ability to acquire an object from the one who is arranging the eiruv. Therefore, a minor child supported by his father cannot be the third party if his father is arranging the eiruv. The Rishonim disagree about whether an adult child who is supported by his father may acquire an eiruv from his father on behalf of other people. Some Rishonim say that he may not, since anything he acquires automatically belongs to his father. A similar disagreement applies to a wife who is supplied with food by her husband. Therefore, a wife or child should not be the ones to acquire the eiruv. If they did, the eiruv is valid bedieved.