Reference for Chullin 70:18

הרי הן כתרומה לטמא שנים ולפסול אחד:

It is treated as terumah, that is, two stages are unclean and one stage invalid.<span class="x" onmousemove="('comment',' I.e., the first and second degrees of uncleanness are each unclean, for each can still pass on its uncleanness, but the third degree is only invalid for it cannot pass on its uncleanness.');">⁸</span>

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