Reference for Chullin 200:9

<big><strong>גמ׳</strong></big> וסבר ר' יהודה איסור חל על איסור

Surely it has been taught: R'Judah says: I might have thought that the carcass of an unclean bird whilst in the gullet should render clothes unclean,<span class="x" onmousemove="('comment',' The carcass of a bird does not render unclean by the usual media of contact or carrying; its only defiling effect is that it renders unclean the clothes of the person who eats of it, and only while he is in the act of swallowing it.');">⁸</span>

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