Reference for Temurah 17:30

קא משמע לן

If where 'a good' [an unblemished hullin] is exchanged for 'a bad' [a blemished animal], in which case an improve is effected,<span class="x" onmousemove="('comment',' As a better animal is being substituted for the dedicated blemished animal.');">²⁰</span>

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