Reference for Chullin 252:40

והוא שהשריץ על פני כולו

A hairbreadth, for then it could be touched with a hair.<span class="x" onmousemove="('comment',' For it is established law that if a person touched the hair of an unclean body or if by his hair he touched an unclean body, in either case he becomes unclean. V. Rashi a.l.');">¹⁸</span>

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