Nedarim 74B

תנן אמר רבי אליעזר: ומה אם אשה שקנה לעצמו ⁠— הרי הוא מיפר נדריה, אשה שהקנו לו מן השמים ⁠— אינו דין שמיפר נדריה? ואי בשעשה בה מאמר, קנה לעצמו הוא! שקנה לעצמו על ידי שמים.

The Talmud raises a difficulty with R' Ami’s explanation of R' Eliezer’s opinion: We learned in the Mishnah that R' Eliezer said: Just as with regard to a woman he acquired for himself through betrothal, he nullifies her vows, so too with regard to a woman acquired for him from Heaven, i.e., the yevama, isn’t it logical that he should be able to nullify her vows? Now if R' Ami’s interpretation is correct, and the Mishnah is referring to a case where a yavam performed levirate betrothal, then it is actually a case where he acquired a woman for himself by performing levirate betrothal. The Talmud answers: Nevertheless, it is a case where he acquired for himself a woman who was imposed upon him by means of Heaven.

תפשוט דבעי רבה: מאמר לבית שמאי, אירוסין עושה או נשואין עושה? תפשוט דנשואין עושה. דאי אירוסין עושה ⁠— הא תנן: נערה המאורסה, אביה ובעלה מפירין נדריה.

The Talmud raises another difficulty with R' Ami’s interpretation, in that if it is correct, you can resolve the dilemma that Rabba raised: Does levirate betrothal, according to Beit Shammai, merely effect betrothal, or does it effect full-fledged marriage? According to R' Eliezer, you can resolve the dilemma by proving that it effects marriage. The proof is as follows: Because if levirate betrothal effects only betrothal, why does the Mishnah mention only the yavam with regard to nullification of vows? Didn’t we learn in a Mishnah (Nedarim 66b) that with regard to a betrothed young woman, her father and her husband together nullify her vows? If levirate betrothal renders her betrothed to the yavam, the father should also be mentioned as a partner in the nullification.