Mishnayos Yevamos Perek 1 Mishnah 2

The mishna explains: How do these women exempt their rival wives? If, for example, his daughter or any one of those women with whom relations are forbidden was married to his brother and this brother had another wife, and the brother died, then just as his daughter is exempt from levirate marriage, so too her rival wife is exempt. If his daughter’s rival wife subsequently went and married his second brother, to whom she is permitted, and he had another wife, and he died childless as well, which means that his wife comes before the first yavam, the daughter’s father, for levirate marriage, then just as his daughter’s rival wife is exempt, so too the rival wife of her rival wife is exempt. The mishna adds: Even if they are one hundred brothers, the same logic applies. If a woman is exempt from levirate marriage because she is the rival wife of a forbidden relative or the rival wife of a rival wife of this kind, and she herself has an additional rival wife, this rival wife is also exempt and in turn exempts her own rival wives from levirate marriage. How so? What are the cases in which if they died their rival wives are permitted? If, for example, one’s daughter or any one of those women with whom relations are forbidden was married to his brother, and this brother had another wife, and then his daughter died or was divorced and afterward his brother died, her rival wife is permitted to him. § The mishna states another principle: And if any of these forbidden relatives was a minor who could refuse her husband, then even if she did not refuse, her rival wife performs ḥalitza and does not enter into levirate marriage. The rival wife may not enter into levirate marriage, as she is the rival wife of a forbidden relative. However, she is not entirely exempt from levirate marriage and must be released by ḥalitza because the marriage of the forbidden relative was not a fully valid marriage, and therefore, by Torah law, the other woman is not considered a rival wife of a forbidden relative.

כֵּיצַד פּוֹטְרוֹת צָרוֹתֵיהֶן. הָיְתָה בִּתּוֹ אוֹ אַחַת מִכָּל הָעֲרָיוֹת הָאֵלּוּ נְשׂוּאָה לְאָחִיו, וְלוֹ אִשָּׁה אַחֶרֶת, וָמֵת, כְּשֵׁם שֶׁבִּתּוֹ פְּטוּרָה, כָּךְ צָרָתָהּ פְּטוּרָה. הָלְכָה צָרַת בִּתּוֹ וְנִשֵּׂאת לְאָחִיו הַשֵּׁנִי, וְלוֹ אִשָּׁה אַחֶרֶת, וָמֵת, כְּשֵׁם שֶׁצָּרַת בִּתּוֹ פְּטוּרָה, כָּךְ צָרַת צָרָתָהּ פְּטוּרָה, אֲפִלּוּ הֵן מֵאָה. כֵּיצַד אִם מֵתוּ צָרוֹתֵיהֶן מֻתָּרוֹת, הָיְתָה בִתּוֹ אוֹ אַחַת מִכָּל הָעֲרָיוֹת הָאֵלּוּ נְשׂוּאָה לְאָחִיו, וְלוֹ אִשָּׁה אַחֶרֶת, מֵתָה בִתּוֹ אוֹ נִתְגָּרְשָׁה, וְאַחַר כָּךְ מֵת אָחִיו, צָרָתָהּ מֻתֶּרֶת. וְכָל הַיְכוֹלָה לְמָאֵן וְלֹא מֵאֲנָה, צָרָתָהּ חוֹלֶצֶת וְלֹא מִתְיַבֶּמֶת: