Eruvin 64A

אם כן, ביטלת תורת עירוב מאותו מבוי!

If so, you have abolished the halakhic category of eiruv from that alleyway. Since from a halakhic perspective it is considered as though only one person lives in that alleyway, there is no need for an eiruv. Consequently, when the residents carry in it without an eiruv, observers will mistakenly think that it is permitted to carry in an alleyway even without an eiruv.

דמערבי. יאמרו עירוב מועיל במקום גוי?! דמכרזינן.

Rav Huna, son of Rav Yehoshua, replied: It is required that they establish an eiruv anyway, as a reminder of the laws of eiruvin, even though it serves no halakhic purpose. Rava retorted that this in turn results in a different problem: Observers will then say that an eiruv is effective even in the place of a non-Jew, even if he does not rent out his domain, which is against the halakha. He replied: We make an announcement to the effect that they are not carrying because of the eiruv, and that it only serves as a reminder.

אכרזתא לדרדקי?!

Rava rejected this option as well: Can we make an announcement for the children? Even if it is assured that all adults present will hear the announcement, how will the children, who do not hear or understand the announcement, know the halakha later in life? Recalling that their fathers established an eiruv in this alleyway, they will think that an eiruv is effective even in the place of a non-Jew. Therefore, one cannot rely on Abaye’s solution.

אלא אמר רבא: ליזיל חד מינייהו, ליקרב ליה, ולשאול מיניה דוכתא ולינח ביה מידי, דהוה ליה כשכירו ולקיטו, ואמר רב יהודה אמר שמואל: אפילו שכירו ואפילו לקיטו ⁠— נותן עירובו ודיו.

Rather, Rava said that the non-Jew’s Jewish neighbors should proceed as follows: Let one of them go and become friendly with the non-Jew, and ask him for permission to make use of a place in his domain, and set something down there, thus becoming like the non-Jew’s hired laborer or harvester. And Rav Yehuda said that Shmuel said: Not only can the non-Jew himself rent out his domain for the purpose of an eiruv, but even his hired laborer, and even his harvester, if he is a Jew, may rent out the space and contribute to the eiruv on his behalf, and this is enough.