Reference for Bava Kamma 202:3

אמר רב כהנא מקולי רביעיות שנו כאן בדם תבוסה דרבנן:

whereas the latter refers to the utensils which were brought there subsequently [after the blood was already absorbed 'in the ground].<span class="x" onmousemove="('comment',' And could no more cause defilement. ');">⁵</span> 'If the blood was absorbed in a garment, we have to see: if on the garment being washed a quarter [of a <i>log</i>] of blood would come out of it,<span class="x" onmousemove="('comment',' As to the way of calculation, v. Rashi and Tosaf. a.l. ');">⁶</span>

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