Reference for Chullin 189:10

אמר רבי

Surely it was taught: Rabbi says: Where the meat stalls [kept by gentiles are supplied with meat by] Israelite butchers, any meat found in the possession of the gentile is permitted! - Here it is different, for the forbidden meat is clearly established.<span class="x" onmousemove="('comment',' He had definitely sold trefah meat to this gentile, and he might have done so to others too, therefore all the meat on the stalls kept by the gentiles is forbidden.');">⁴</span>

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