Reference for Yevamot 236:9
דאע"ג דאיסורא דרבנן עבד קניס תנא גזל להודיעך כחו דרבי טרפון דאע"ג דאיסורא דאורייתא עבד לא קניס:
<b><i>MISHNAH</i></b>. A WOMAN WHO WENT WITH HER HUSBAND TO A COUNTRY BEYOND THE SEA, HER SON ALSO [GOING] WITH THEM, AND WHO CAME BACK AND STATED, 'MY HUSBAND DIED AND AFTERWARDS MY SON DIED', IS BELIEVED.<span class="x" onmousemove="('comment',' And is exempt from levirate marriage and halizah. Her statement is accepted since thereby she is merely confirming the status in which she found herself before her departure. At that time she had a son who exempted her from the levirate bond; and now that her husband died before that son she is still entitled to the same exemption. Her admission of her son's death does not affect her status, since she is the only source of the information, and as her word is accepted in respect of the death it must be similarly accepted in respect of its date. ');"><sup>18</sup></span> [IF, HOWEVER, SHE STATED.] 'MY SON DIED AND AFTERWARDS MY HUSBAND DIED'.<span class="x" onmousemove="('comment',' So that she is in consequence subject to the levirate bond. ');"><sup>19</sup></span> SHE IS NOT BELIEVED,<span class="x" onmousemove="('comment',' Because her assertion would alter the status in which she was confirmed prior to her departure. Such alteration cannot be authorized in view of the possibility that her report might be due to a desire to marry the levir. ');"><sup>20</sup></span>