Reference for Chullin 273:25

הגוזז את העזים פטור ושוטף את הרחלים חייב

Sheep with hard wool are exempt from the law of the first of the fleece, since it is written: And if he were not warmed with the fleece of my sheep.<span class="x" onmousemove="('comment',' Job. XXXI, 20. Hence only soft wool which gives warmth is subject to the law of the first of the fleece, but not hard wool; this rule is established by reason of the analogy through the expression 'fleece'.');">¹⁹</span>

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