Reference for Chullin 279:37

הכא במאי עסקינן בעוף שהרג את הנפש היכי דמי

R'Papa said, [The expression 'clean'] serves to exclude birds that were obtained in exchange for an idol, for it is written: And become a devoted thing like unto it;<span class="x" onmousemove="('comment',' Deut. VII, 26.');">²⁷</span>

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