Reference for Eruvin 167:15

תא שמע אנשי חצר ואנשי עלייה ששכחו ולא עירבו אנשי חצר משתמשין בעשרה התחתונים ואנשי עלייה משתמשין בעשרה העליונים כיצד זיז יוצא מן הכותל למטה מעשרה לחצר למעלה מעשרה לעלייה

For if we had been informed of the law in the case of the ROCK only, the ruling might have been presumed to apply to that alone, since no preventive measure in that case could be called for,<span class="x" onmousemove="('comment',' Lit., 'there is not (reason) to make a preventive measure');">³⁰</span> but that in the case of a cistern a preventive measure<span class="x" onmousemove="('comment',' Forbidding its use.');">³¹</span> should be enacted, since it might sometimes be full of properly prepared fruit,<span class="x" onmousemove="('comment',' Which may be handled on the Sabbath and which might, therefore, be removed during the Sabbath day.');">³²</span>

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