Mishnayos Kesuvos Perek 2 Mishnah 5

With regard to a woman who said: I was a married woman and now I am a divorcée, she is deemed credible and permitted to remarry, as the mouth that prohibited and established that she was married is the mouth that permitted, and established that she is divorced. However, if there are witnesses that she was a married woman, and she says: I am a divorcée, she is not deemed credible. Similarly, with regard to a woman who said: I was taken captive but I am pure, as I was not raped in captivity, she is deemed credible and permitted to marry a priest, as the mouth that prohibited and established that she was taken captive is the mouth that permitted and established that she was not defiled. But if there are witnesses that she was taken captive, and she says: I am pure, she is not deemed credible. And if witnesses came after she married, this woman need not leave her husband.

הָאִשָּׁה שֶׁאָמְרָה אֵשֶׁת אִישׁ הָיִיתִי וּגְרוּשָׁה אָנִי, נֶאֱמֶנֶת, שֶׁהַפֶּה שֶׁאָסַר הוּא הַפֶּה שֶׁהִתִּיר. וְאִם יֵשׁ עֵדִים שֶׁהָיְתָה אֵשֶׁת אִישׁ וְהִיא אוֹמֶרֶת גְּרוּשָׁה אָנִי, אֵינָהּ נֶאֱמֶנֶת. אָמְרָה נִשְׁבֵּיתִי וּטְהוֹרָה אָנִי, נֶאֱמֶנֶת, שֶׁהַפֶּה שֶׁאָסַר הוּא הַפֶּה שֶׁהִתִּיר. וְאִם יֵשׁ עֵדִים שֶׁנִּשְׁבֵּית וְהִיא אוֹמֶרֶת טְהוֹרָה אָנִי, אֵינָהּ נֶאֱמֶנֶת. וְאִם מִשֶּׁנִּשֵּׂאת בָּאוּ עֵדִים, הֲרֵי זוֹ לֹא תֵצֵא: