Mishnayos Yevamos Perek 14 Mishnah 4

However, if two brothers, one of whom is a deaf-mute and other one halakhically competent, were married to two halakhically competent sisters, and the deaf-mute married to the halakhically competent sister died, what should the halakhically competent brother married to the halakhically competent sister do? His brother’s wife is released without levirate marriage or ḥalitza, due to the prohibition with regard to a wife’s sister. If the halakhically competent brother married to the halakhically competent sister died, what should the deaf-mute brother married to the halakhically competent sister do? He divorces his wife with a bill of divorce, as his wife’s sister came before him for levirate marriage by Torah law, and the legal status of her marriage and her levirate marriage is higher than his own marriage, which applies only by rabbinic law. And his brother’s wife is forbidden to him forever, and there is no remedy for her. He cannot marry her, as by rabbinic law she is the sister of his ex-wife, nor can he exempt her by means of ḥalitza, as he is a deaf-mute.

שְׁנֵי אַחִים, אֶחָד חֵרֵשׁ וְאֶחָד פִּקֵּחַ, נְשׂוּאִים לִשְׁתֵּי אֲחָיוֹת פִּקְחוֹת, מֵת חֵרֵשׁ בַּעַל הַפִּקַּחַת, מַה יַּעֲשֶׂה פִקֵּחַ בַּעַל הַפִּקַּחַת, תֵּצֵא מִשּׁוּם אֲחוֹת אִשָּׁה. מֵת פִּקֵּחַ בַּעַל הַפִּקַּחַת, מַה יַּעֲשֶׂה חֵרֵשׁ בַּעַל פִּקַּחַת, מוֹצִיא אִשְׁתּוֹ בְגֵט, וְאֵשֶׁת אָחִיו אֲסוּרָה לְעוֹלָם.