Reference for Chullin 228:3

ומה במקום שלא נאסר פרי עם פרי בשחיטה נאסר פרי עם האם בשחיטה

- as in the case of slaughtering - the fruit with the dam is forbidden, how much more, therefore, where the fruit is forbidden with the fruit<span class="x" onmousemove="('comment',' The kid and the mother's milk are each the 'fruit' of the she-goat.');">²</span>

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