Reference for Taanit 40:9

מאי הוה עובדיה דרב אדא בר אהבה כי הא דאתמר שאלו תלמידיו (את רבי זירא ואמרי לה) לרב אדא בר אהבה במה הארכת ימים אמר להם מימי לא הקפדתי בתוך ביתי ולא צעדתי בפני מי שגדול ממני

Are not 'sound buildings' same as 'those that are not likely to fall in'? And are not those already dilapidated' the same as 'those likely to fall in'? - It is necessary [to distinguish between them] when for instance they collapsed because of their excessive height, or, when they stood on the bank of a river.<span class="x" onmousemove="('comment',' Though they were sound they were liable to fall, because of their height or because of the water washing away the foundations.');">³</span>

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