Reference for Nedarim 181:4

אמר ליה רבא אדרבה אפי' למשנה ראשונה דקתני מהימנא התם משום דלא עבידא לבזויי נפשה אבל הכא דזמנין דתקיף לה מן גברא מעיזה ומעיזה

which teaches that she is not believed, it is [only] there that she may lie, in the knowledge that her husband does not know;<span class="x" onmousemove="('comment',' Whether her statement is true. ');">⁶</span> but with respect to 'You have divorced me,' of [the truth of] which he must know, she is believed, for there is a presumption [that] no woman is brazen in the presence of her husband.<span class="x" onmousemove="('comment',' I.e., she would not be brazen enough to tell such a lie in his presence, wherefore she is believed. ');">⁷</span>

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