Reference for Pesachim 168:9

כדתניא ר' ישמעאל בנו של ר' יוחנן בן ברוקה אומר אבר שיצא מקצתו ושברו אין בו משום שבירת העצם

Now if you think that the breaking of the bone by daylight is permitted, then the thigh-bone too, let us break it during the day, extract the marrow, and register for it? - Abaye can answer you: Yet even according to your view,<span class="x" onmousemove="('comment',' Sc. that this is forbidden.');">⁸</span> let us still take a glowing coal after nightfall, place it upon it, bur and extract the marrow and register for it?

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