Reference for Chullin 56:3

וושט אין לו בדיקה מבחוץ אלא מבפנים

His son, R'Joseph, said to him: We could first examine the windpipe and then cut it,<span class="x" onmousemove="('comment',' And this in itself would be sufficient to render the slaughtering valid.');">²</span>

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