Reference for Yevamot 238:15

בעי רבא מאי טעמא דרבי אלעזר משום דקסבר צרה מעידה לחברתה או דלמא משום דהיא לא מקלקלא נפשה

WHILE SHE WHO HAD NO WITNESSES IS PERMITTED.<span class="x" onmousemove="('comment',' To marry any stranger; since she herself is believed in respect of the death of her husband while in respect of the death of the levir the evidence of the witnesses is available. ');">³⁷</span> IF THE ONE HAD CHILDREN AND THE OTHER HAD NO CHILDREN,<span class="x" onmousemove="('comment',' And neither had witnesses. ');">³⁸</span> SHE WHO HAD CHILDREN<span class="x" onmousemove="('comment',' Who exempt their mother from the levirate bond. ');">³⁹</span>

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