Reference for Eruvin 69:18
וצריכי דאי תנא נתגלגל משום דליתא גביה אבל נפל עליו גל דאיתיה גביה אימא ליהוי עירוב
[an area of] four cubits.<span class="x" onmousemove="('comment',' Which is regarded as his abode. As his 'erub did not roll beyond his acquired abode it must be regarded as effective.');"><sup>60</sup></span> OR IF A HEAP FELL ON IT etc. Having been presumed that, if desired, [the 'erub] could be taken out,<span class="x" onmousemove="('comment',' Without the use of implements entailing work that is Pentateuchally forbidden on the Sabbath.');"><sup>61</sup></span> must it be assumed<span class="x" onmousemove="('comment',' Since the 'erub is deemed ineffective on account, apparently, of the Rabbinical prohibition involved in the removal of the stones that covered it.');"><sup>62</sup></span> that our Mishnah is not in agreement with Rabbi, for if [it were suggested to be] in agreement with Rabbi [the difficulty would arise]: Did he not lay down that any work that was only Rabbinically prohibited was not forbidden as a preventive measure [on the Sabbath eve] at twilight?<span class="x" onmousemove="('comment',' And since the validity of an 'erub, as explained Supra, is dependent on its efficacy at twilight, when the removal of stones (being only Rabbinically forbidden on the Sabbath) is according to Rabbi permitted, the 'erub spoken of in our Mishnah would have been effective.');"><sup>63</sup></span>