Reference for Yevamot 61:12

מידי דהוה אנכסי דבר שטיא דבר שטיא זבין נכסי אתו בי תרי ואמרי כשהוא חלים זבין ואתו בי תרי ואמרו כשהוא שוטה זבין ואמר רב אשי אוקי תרי להדי תרי

where the doubt involved is only Rabbinical.<span class="x" onmousemove="('comment',' Hence, in the matter of betrothal, where the rival enjoyed the status of permissibility to the levir, the law that halizah is required in the case of such contradictory evidence could well be applied, since she cannot be deprived of her status by the evidence of the single witness who states that the token of betrothal was nearer to her. In the case of divorce, however, where the rival has the status of permissibility to marry any stranger, the law that halizah is required in the case of contradictory evidence of two single witnesses could not be applied. since the evidence of one witness is not sufficient to deprive her of that right. particularly as it can also be claimed that were she required to perform halizah she might be taken in levirate marriage also. ');">³¹</span> Whence is it proved that our Mishnah speaks of one group? — On analogy with betrothal:<span class="x" onmousemove="('comment',' Divorce and betrothal being mentioned side by side in this Mishnah. ');">³²</span> As in betrothal only one group is involved so also in divorce<span class="x" onmousemove="('comment',' Had it been included in our Mishnah. ');">³³</span> one group only could be involved. Whence is it known that in betrothal itself only one group is involved? Is it not possible that it involves two groups of witnesses! — If two groups of witnesses had been involved, she would have been allowed to contract the levirate marriage, and no wrong would have been done.<span class="x" onmousemove="('comment',' Since the evidence of one pair would have been sufficient to confirm the rival in her status of permissibility to the levir. Hence, as levirate marriage was forbidden it cannot be a case of two groups of witnesses. ');">³⁴</span> Witnesses stand and declare that it<span class="x" onmousemove="('comment',' The token of betrothal. ');">³⁵</span> was nearer to her,<span class="x" onmousemove="('comment',' Thus presenting a Pentateuchal doubt (cf. supra p. 195. n. 9). ');">³⁶</span> and you say that she may be taken in levirate marriage and no wrong will be done!<span class="x" onmousemove="('comment',' This, surely. might result in the breach of a Pentateuchal law! ');">³⁷</span> Furthermore, even where two groups of witnesses are involved the doubt is only Rabbinical, since it might be said 'Put one pair against the other and let the woman retain her original status'!<span class="x" onmousemove="('comment',' Why. then, even in the case of divorce itself, when the two groups of witnesses cancel each other, should the rival, who was hitherto in a state of permissibility to marry anyone. be required to perform halizah! ');">³⁸</span> This indeed is similar to [the incident with] the estate of a certain lunatic. For a certain lunatic once sold some property. and a pair of witnesses came and declared that he had effected the sale while in a sound state of mind, and another pair came and declared that the sale was effected while he was in a state of lunacy. And R. Ashi said: Put two against two

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