Reference for Zevachim 189:1

מדרבנן הוא:

That is by Rabbinical law [only].<span class="x" onmousemove="('comment',' As a preventive measure, lest one does not tear the greater part of it. but Scripturally it is clean, and here the Rabbis waived this measure in order that the precept of washing may be fulfilled.');">¹</span>

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