TT #665 · 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 Yevamot 39a.
TT lemma: וּלְקָחָהּ לוֹ לְאִשָּׁה.
יָכוֹל כְּשֵׁם שֶׁהַבִּיאָה גּוֹמֶרֶת בָּהּ כָּךְ הַמַּאֲמָר גּוֹמֵר בָּהּ? תַּלְמוּד לוֹמַר וְיִבְּמָהּ – אוֹרְעָהּ כָּל הַפָּרָשָׁה כֻּלָּהּ לְיִבּוּם: הַבִּיאָה גּוֹמֶרֶת בָּהּ וְאֵין הַמַּאֲמָר גּוֹמֵר בָּהּ.
English: Might one think that just as bi’ah completes the acquisition, so ma’amar completes it? Scripture says “and he shall perform the duty of a husband’s brother” — the entire passage is oriented toward yibbum: bi’ah completes it, ma’amar does not.
On the daf / in context: Ma’amar creates a partial bond that forbids her to the other brothers but does not finish the acquisition.
Derash limiting the effect of ma’amar.
Ma’amar does not complete yibbum; only bi’ah does. Ma’amar’s effect is to prohibit her to the other brothers.