Reference for Shabbat 201:4

מתקיף לה רב יוסף ולא שמיעא להו להא דאמר רב יהודה אמר רב ומטו בה משום רבי חייא ותני עלה וחכמים פוטרין אמר ליה אביי ואת לא תסברא והתניא עמוד ברה"ר גבוה עשרה ורחב ד' ואין בעיקרו ד' ויש בקצר שלו ג' וזרק ונח על גביו חייב אלמא אמרינן גוד אחית מחיצתא הכא נמי גוד אחית מחיצתא

so here too let us say, Stretch and bring the partition down? R. Joseph demurred to this, Yet did they not hear what was said by Rab Judah in Rab's name, which some trace to R. Hiyya: And it was taught thereon, But the Sages exempt [him]?<span class="x" onmousemove="('comment',' Which proves that the majority reject this legal fiction. ');">⁹</span> Said Abaye to him: And do you not hold thus? But it was taught: If a pillar in the street [is] ten [handbreadths] high and four broad, but its base is not four, and this narrow portion is three [in height],<span class="x" onmousemove="('comment',' So that the principle of being accounted as joined to the ground from the level which gives a breadth of four does not operate. ');">¹⁰</span> and one throws [an article] and it alights upon it, he is liable: this proves that we say, Stretch and bring the partitions down;<span class="x" onmousemove="('comment',' Otherwise the base would be disregarded, and the sides above would count as partitions suspended in the air, which cannot form a private domain. ');">¹¹</span>

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