Reference for Eruvin 167:14

ול"ל למיתנא בור ול"ל למיתנא סלע צריכא דאי אשמעינן סלע דליכא למיגזר אבל בור ליגזור זמנין דמליא פירות מתוקנין צריכא

But<span class="x" onmousemove="('comment',' If it is to be assumed that the cistern was full of fruit that cannot be diminished on the Sabbath as a rock that cannot be diminished.');">²⁸</span> why should it be necessary to mention both CISTERN and ROCK?<span class="x" onmousemove="('comment',' Seeing that one could easily be inferred from the other.');">²⁹</span> - Both are required.

Jastrow