975. Vague vs. Specific Instructions

Eiruvin 6:23

If an individual or a group tells someone to go make an eiruv for them and that person does so, and he chooses the direction to make the eiruv, the eiruv is valid. They rely upon it because they didn’t specify in which direction he should make it. If a person instructs his agent to make an eiruv for him using dates and the agent uses figs or vice versa, the eiruv is invalid. Similarly, if he directs that the eiruv be placed in a cabinet but the agent put it in a bird coop or vice versa, or if he directed that it be placed in the house but it was placed in the attic or vice versa, the eiruv is invalid. But if he simply told the agent to make an eiruv without any specifications, then the eiruv is valid whether the agent used figs or dates, or placed it in the house or the attic.

Eiruvin 6:24

Just as we recite a bracha when making an eiruv for a courtyard or a shittuf for an alley, we recite a bracha when making eiruvei techumin. After reciting the bracha, one should say, “By means of this eiruv, it will be permissible for me to travel 2,000 cubits in every direction from this spot.” If one is making an eiruv on behalf of a group, he should say, “By means of this eiruv, it will be permissible for (names)...” or “…for the people of this community...” or “…for the residents of this city….”