Reference for Gittin 145:11

אתא לקמיה דרבינא א"ל זיל שפי ליה דהא קבילת עלך כל אונסא דמתיליד א"ל רב אחא בר תחליפא לרבינא אונסא דלא שכיח הוא

A certain man sold a field to his neighbour, guaranteeing him against any accident that might happen to it. Eventually they [the Government] turned a river through it. He consulted Rabina, who said to him, You must go and clear it for him, since you have guaranteed him against any accident which may happen to it. Thereupon R. Aha b. Tahalifa remarked to Rabina: It is an exceptional kind of accident. Various opinions were taken<span class="x" onmousemove="('comment',' Lit., 'the matter was circulated'. ');">¹⁰</span>

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