Reference for Bekhorot 53:15

רבה מבטלה ברוב ואוכל לה בימי טומאתו

of hullin with one natla of terumah, and after that he would add one [natla] and take one.<span class="x" onmousemove="('comment',' And proceeded to act thus until all the terumah was neutralized, there being always a greater quantity of hullin to neutralize the terumah. (R. Gershom.)');">¹²</span>

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