TT #718 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:07
And if the man does not desire to take his yevamah, then his yevamah shall go up to the gate to the elders and say: “My husband’s brother refuses to establish a name for his brother in Israel; he will not perform the duty of a husband’s brother for me.”
Torah Temimah points to Yevamot 79b.
TT lemma: לְהָקִים לְאָחִיו שֵׁם.
סְרִיס אָדָם חוֹלֵץ וְחוֹלְצִין לְאִשְׁתּוֹ – וְאַף עַל גַּב דִּכְתִיב לְהָקִים לְאָחִיו שֵׁם וְהַאי לָאו בַּר הָכִי הוּא, מִשּׁוּם דִּשְׁעַת הַכֹּשֶׁר דְּמֵעִיקָּרָא מִילְּתָא הִיא.
English: A man-made eunuch performs chalitzah and his wife receives chalitzah — even though it is written “to establish a name for his brother” and he is not capable of that, because the prior state of fitness is what matters.
On the daf / in context: A man who was once capable of procreation remains within the law of chalitzah even after becoming a eunuch by human action.
Derash preserving the status of a former capable man.
A man who became a eunuch through human action (or his widow) is still subject to chalitzah because he once had the capacity to establish a name.