Reference for Bava Metzia 186:7

אי הכי מאי איריא שומר שכר אפי' שומר חנם נמי דהא מר הוא דאמר שומר חנם שהיה לו לקדם ברועים ובמקלות ולא קידם חייב שומר חנם בחנם שומר שכר בשכר

Surely it means that he entered [the town] when other people generally do? — No. He entered when people do not generally enter. If so, why is he not responsible? Where there is negligence in the beginning, though subsequently an accident supervenes, he is liable!<span class="x" onmousemove="('comment',' V. supra, 42a. Thus here too, he might have averted some slight mishap, had he been at his post; and therefore by deserting it he displayed negligence and should be liable, notwithstanding that subsequently the damage was unpreventable. ');">⁶</span>

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