Reference for Yevamot 216:14
ברם כך שאלו הרי היתה אשת אחי אמו שהיא שנייה לו ונשאה אחיו מאביו ומת מהו שתמאן השתא ותעקרינהו לנישואין קמאי ותתייבם צרתה יש מיאון לאחר מיתה במקום מצוה או לא
the following <i>halachah</i> was inquired for: If a minor left her first husband with a letter of divorce and her second husband through <i>mi'un</i>, may she return to her first husband? They hired a man for four hundred <i>zuz</i>,<span class="x" onmousemove="('comment',' V. Glos. ');"><sup>31</sup></span> and [through him] they addressed the enquiry to R. Akiba in prison,<span class="x" onmousemove="('comment',' The payment of the exorbitant sum of four hundred zuz for obtaining the required ruling recalled to Rab's mind the text of Lamentations quoted. ');"><sup>32</sup></span> and he stated that she was forbidden.<span class="x" onmousemove="('comment',' To return to her first husband. ');"><sup>33</sup></span>