Reference for Chullin 181:21

דתניא

Now since it says: 'From two thighs of two animals' it is obvious that the prohibited one of each is intended;<span class="x" onmousemove="('comment',' I.e., the right thigh of each animal, for otherwise it would have been sufficient to speak of the two thighs of the one animal.');">¹²</span>

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