TT #685 · 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: וְהָיָה הַבְּכוֹר אֲשֶׁר תֵּלֵד.
וְהָיָה הַבְּכוֹר אֲשֶׁר תֵּלֵד – יָכוֹל בֵּן הוּא? תַּלְמוּד לוֹמַר יָקוּם עַל שֵׁם אָחִיו הַמֵּת – מִכָּאן שֶׁאֵין הַבֵּן יוֹרֵשׁ אֶת אָחִי אָבִיו בִּמְקוֹם אָבִיו.
English: “And it shall be that the firstborn that she bears” — might one think this refers to a son born of the yibbum? Scripture says “he shall succeed to the name of his dead brother” — from here we learn that the son does not inherit his father’s brother in place of his father.
On the daf / in context: The verse is applied to the yavam’s inheritance rights rather than to a child born of the union.
Derash redirecting “the firstborn” to the yavam.
The language “the firstborn that she bears” is expounded of the yavam’s right to the inheritance, not of a child born from the yibbum.