Reference for Niddah 79:33

מסתברא מבכור הוה ליה למילף שכן אמו מאמו

[the laws in the context apply only to] one who is undoubtedly male or undoubtedly female but not to a <i>tumtum</i> or an hermaphrodite, hence we were informed that the law applies to the latter also. And R. Simeon?<span class="x" onmousemove="('comment',' Whence does he deduce the last mentioned law? ');">³¹</span>

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