Mishnayos Yevamos Perek 13 Mishnah 7

If two brothers are married to two minor sisters, and the husband of one of them dies childless, this widowed girl shall be exempt from levirate marriage due to her status as a forbidden relative, as one is prohibited from marrying the sister of his wife. The same halakha applies to two deaf-mute women, whose status is like that of two minors in this matter, as their marriages are valid by rabbinic law. And if two brothers were married to two sisters, one of them an adult and the other a minor, and the husband of the minor dies, the minor shall leave due to her status as the sister of a wife, as in the first case in the mishna. But if the husband of the adult dies, it generates a Torah obligation of levirate marriage, which is not abrogated by the rabbinic prohibition proscribing the yevama as his wife’s sister. This prohibition is by rabbinic law, because marriage to a minor is rabbinic in origin. What does one do under such circumstances? Rabbi Eliezer says: We instruct the minor, i.e., his wife, to refuse him, so that her marriage is dissolved and he may then enter into levirate marriage with her adult sister, the widow of his childless brother. Rabban Gamliel says: If the minor refuses of her own accord, her refusal is valid. And if not, she should wait until she reaches majority, whereupon her marriage is valid by Torah law, and that widowed adult sister shall be exempt from levirate marriage due to her status as the sister of a wife. Rabbi Yehoshua says: When the brother married to the adult sister dies, leaving the brother married to the minor, woe [ee] to him for his wife, woe to him for his brother’s wife. Under these circumstances, he loses both women: He must release his own wife with a bill of divorce and his brother’s wife by performing ḥalitza. He cannot stay married to his wife because she is the sister of his yevama, and he cannot enter into levirate marriage with the yevama even after divorcing his wife, because the yevama is his wife’s sister. The principle that one is completely absolved from levirate marriage when the potential yevama is a forbidden relative does not apply because Torah law does not recognize his marriage to his minor wife. That marriage’s rabbinic sanction does not suffice to render the yevama, his wife’s sister, a forbidden relative who is not a candidate for levirate marriage.

שְׁנֵי אַחִין נְשׂוּאִין לִשְׁתֵּי אֲחָיוֹת יְתוֹמוֹת קְטַנּוֹת, וּמֵת בַּעְלָהּ שֶׁל אַחַת מֵהֶן, תֵּצֵא מִשּׁוּם אֲחוֹת אִשָּׁה. וְכֵן שְׁתֵּי חֵרְשׁוֹת גְדוֹלָה וּקְטַנָּה, מֵת בַּעְלָהּ שֶׁל קְטַנָּה, תֵּצֵא הַקְּטַנָּה מִשּׁוּם אֲחוֹת אִשָּׁה. מֵת בַּעְלָהּ שֶׁל גְּדוֹלָה, רַבִּי אֱלִיעֶזֶר אוֹמֵר, מְלַמְּדִין אֶת הַקְּטַנָּה שֶׁתְּמָאֵן בּוֹ. רַבָּן גַּמְלִיאֵל אוֹמֵר, אִם מֵאֲנָה, מֵאֲנָה. וְאִם לָאו, תַּמְתִּין עַד שֶׁתַּגְדִּיל, וְתֵצֵא הַלָּזוּ מִשּׁוּם אֲחוֹת אִשָּׁה. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, אִי לוֹ עַל אִשְׁתּוֹ, וְאִי לוֹ עַל אֵשֶׁת אָחִיו. מוֹצִיא אֶת אִשְׁתּוֹ בְגֵט, וְאֵשֶׁת אָחִיו בַּחֲלִיצָה: