Reference for Eruvin 51:2

למחר איתיביה רבינא לרבא עיר חדשה מודדין לה מישיבתה וישנה מחומתה

On the following day, however, Rabina raised an objection against Raba: [The Sabbath limits of] a new town are measured from its inhabited quarter<span class="x" onmousemove="('comment',' The area between the inhabited quarter and the town walls is regarded in this respect as being outside the town.');">³</span> and of all old one from its town wall.

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