Reference for Shabbat 200:5

רב אשי אמר איצטריך ס"ד אמינא ה"מ היכא דהוה ד' אבל היכא דלא הואי ארבעה מיפסעי פסעי ליה ואזדא רב אשי לטעמיה דאמר רב אשי האי מאן דזריק ונח אגודא דגמלא מיחייב שהרי רבים בוקעין בו:

but where it is not four, one steps over it.<span class="x" onmousemove="('comment',' And thus avoids it. ');">¹⁰</span> Now, R. Ashi is consistent with his opinion. For R. Ashi said: If one throws [an object] and it alights on the junction of a landing bridge.<span class="x" onmousemove="('comment',' Perhaps where the bridge joins the quay. ');">¹¹</span> he is culpable, since many pass across it.<span class="x" onmousemove="('comment',' Though many, on the other hand, step over it, it does not on that account cease to be ground publicly used, and the same applies above. ');">¹²</span>

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