TT #698 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:06
And it shall be that the firstborn that she bears shall succeed to the name of his dead brother, so that his name shall not be blotted out from Israel.
Torah Temimah points to Yevamot 24a.
TT lemma: וְלֹא יִמָּחֶה שְׁמוֹ.
וְלֹא יִמָּחֶה שְׁמוֹ – פְּרָט לְסָרִיס שֶׁשְּׁמוֹ מָחוּי.
English: “So that his name shall not be blotted out” — excluding a saris (eunuch) whose name is already blotted out.
On the daf / in context: A man who is a congenital eunuch has no prospect of establishing a name; therefore neither he nor his widow is subject to yibbum or chalitzah.
Mi’ut excluding the saris.
A congenital eunuch and his widow are exempt from yibbum and chalitzah.