TT #653 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:05
When brothers dwell together and one of them dies and has no son, the wife of the dead shall not be outside to a strange man; her husband’s brother shall come upon her and take her to himself as a wife and perform the duty of a husband’s brother for her.
Torah Temimah points to Sifrei / Yevamot.
TT lemma: לֹא תִהְיֶה אֵשֶׁת הַמֵּת הַחוּצָה.
אֵשֶׁת אֶחָד מִתְיַבֶּמֶת וְלֹא אֵשֶׁת שְׁנַיִם.
English: The wife of one (brother) is subject to yibbum, but not the wife of two.
On the daf / in context: When a woman is under zikah to two yavams simultaneously (complex cases of successive deaths), the verse’s singular language excludes yibbum.
Mi’ut from the singular “the wife of the dead.”
A woman subject to the zikah of two brothers at once is not taken in yibbum.