Reference for Eruvin 179:10

ושמואל אמר אין מטלטלין בו אלא בד' אמות קשיא דשמואל אדשמואל התם לא הוי יותר מבית סאתים הכא הוי יותר מבית סאתים והני מחיצות למטה עבידן למעלה לא עבידן והוה כקרפף יתר מבית סאתים שלא הוקף לדירה וכל קרפף יותר מבית סאתים שלא הוקף לדירה אין מטלטלין בו אלא בד'

There the walls are undistinguishable<span class="x" onmousemove="('comment',' One standing on any of the roofs cannot see them since they are covered by the roofs. Hence it is that the principle of upward extensions cannot be applied and the roofs, according to the Rabbis, impose restrictions upon each other.');">⁴⁰</span> but, here, the walls<span class="x" onmousemove="('comment',' Of (a) the detached house, according to the Rabbis, and (b) those of the outermost houses according to R. Meir.');">⁴¹</span> are distinguishable.<span class="x" onmousemove="('comment',' They can well be seen from (a) the roof or (b) the roofs. The principle of upward extension is, therefore, applicable.');">⁴²</span> But since 'Samuel ruled: Objects may be moved only within four cubits',<span class="x" onmousemove="('comment',' From which it follows that he does not hold the principle of upward extension.');">⁴³</span> does not a contradiction arise between two rulings of Samuel?<span class="x" onmousemove="('comment',' Cf. Supra n. 9 mut. mut.');">⁴⁴</span>

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