Commentary for Eruvin 9:8

אמר לך אביי התם סוף מבוי הכא תחלת מבוי אי איכא ארבע אמות אין אי לא לא

ten [cubits].<span class="x" onmousemove="('comment',' A gap wider than ten cubits cannot be regarded as a doorway and destroys, therefore, the Sabbatic ritual validity of the alley.');">²⁸</span> If, however, [there was] no [such strip<span class="x" onmousemove="('comment',' Sc. if it was either wanting altogether or of less than four handbreadths in width.');">²⁹</span> there] it is permissible [to regard the alley as ritually fit, if the br was] less than three [handbreadths wide],<span class="x" onmousemove="('comment',' Such a narrow breach may be regarded as non-existent (v. Glos. s.v. labud) and the wall is deemed to be virtually intact.');">³⁰</span> [but if it was] three [handbreadths wide]<span class="x" onmousemove="('comment',' And people are consequently likely to use the gap as a short cut thus neglecting the use of the main entrance.');">³¹</span> this is not permissible.<span class="x" onmousemove="('comment',' Lit., 'it does not permit', since (v. previous note) the ritual validity of the main entrance has thereby been destroyed.');">³²</span>

Rashi on Eruvin