א יְבָמָה שֶׁאֵינָהּ רְאוּיָה לְהִתְיַבֵּם בִּשְׁעַת נְפִילָה, מִשּׁוּם אִסוּר עֶרְוָה, אֲסוּרָה עוֹלָמִית, אֲפִלּוּ אִם יִפְקַע הָאִסוּר. כְּגוֹן שְׁנֵי אַחִים שֶׁנְּשׂוּאִים שְׁתֵּי אֲחָיוֹת, וּמֵת אֶחָד מֵהֶם, וְנָפְלָה אִשְׁתּוֹ לִפְנֵי הַשֵּׁנִי שֶׁנָּשׂוּי אֲחוֹתָהּ, אֲפִלּוּ אִם תָּמוּת אִשְׁתּוֹ אַחַר כָּךְ, שֶׁפָּקַע אִסוּר אֲחוֹת אִשָּׁה, אֲפִלּוּ הָכִי אֲסוּרָה. וַאֲפִלּוּ נָפְלָה לְפָנָיו פַּעַם אַחֶרֶת אַחֲרֵי מוֹת אִשְׁתּוֹ, כְּגוֹן שֶׁהָיָה לָהֶם אָח שְׁלִישִׁי שֶׁלֹּא הָיְתָה עֶרְוָה עָלָיו, וּכְּנָסָהּ, וּמֵתָה אִשְׁתּוֹ שֶׁל זֶה שֶׁהָיָה נָשׂוּי אֲחוֹתָהּ, וּמֵת הַשְּׁלִישִׁי שֶׁכְּנָסָהּ, וְחָזַר וְנָפְלָה לְפָנָיו, אֲסוּרָה לוֹ. לָא שְׁנָא מֵתָה אִשְׁתּוֹ קֹדֶם שֶׁכָּנַס הַשְּׁלִישִׁי, לֹא שְׁנָא מֵתָה אַחַר שֶׁכָּנַס, אַף עַל פִּי שֶׁלֹּא הָיְתָה אֲסוּרָה עָלָיו בִּשְׁעַת נְפִילָה אַחֲרוֹנָה, אֲפִלּוּ הָכִי אֲסוּרָה לוֹ הִיא וְצָרָתָהּ, כְּגוֹן שֶׁהָיָה אִשָּׁה אַחֶרֶת לָאָח הַשְּׁלִישִׁי, כֵּיוָן שֶׁהָיְתָה אֲסוּרָה לוֹ בִּשְׁעַת נְפִילָה רִאשׁוֹנָה. אֲבָל אִם הָיְתָה מֻתֶּרֶת לוֹ בִּשְׁעַת נְפִילָה, אֲפִלּוּ אִם תֵּאָסֵר אַחַר כָּךְ, אִם פָּקַע הָאִסוּר, חוֹזֶרֶת לְהֶתֵּרָהּ. כֵּיצַד, שְׁלשָׁה אַחִים שְׁנַיִם מֵהֶם נְשׂוּאִים שְׁתֵּי אֲחָיוֹת, וּמֵת אֶחָד מֵהֶם, וְנִזְקְקָה אִשְׁתּוֹ לַשְּׁלִישִׁי שֶׁאֵינוֹ נָשׂוּי אֲחוֹתָהּ, וְלֹא הִסְפִּיק לְכָנְסָהּ עַד שֶׁמֵּת הָאָח הַשֵּׁנִי שֶׁהָיָה נָשׂוּי הָאַחֶרֶת, וַהֲרֵי שְׁתֵּיהֶן אֲסוּרוֹת עָלָיו, מֵתָה הָאַחֲרוֹנָה, חָזְרָה הָרִאשׁוֹנָה לְהֶתֵּרָהּ, כֵּיוָן שֶׁהָיְתָה מֻתֶּרֶת בִּשְׁעַת נְפִילָה, אַף עַל פִּי שֶׁנֶּאֶסְרָה בֵּינְתַיִם. אֲבָל אִם מֵתָה הָרִאשׁוֹנָה, לֹא הֻתְּרָה הָאַחֲרוֹנָה, כֵּיוָן שֶׁהָיְתָה אֲסוּרָה בִּשְׁעַת נְפִילָה. וְכֵן אִם הָיוּ שָׁם עוֹד אַחִים, וְקָדַם אֶחָד מֵהֶם וְחָלַץ לָאַחֲרוֹנָה, אוֹ שֶׁהָיְתָה הָרִאשׁוֹנָה אֲסוּרָה לְאֶחָד מֵהָאַחִים, וְיִבֵּם אֶת הָאַחֲרוֹנָה, שֶׁהֲרֵי מֻתֶּרֶת לוֹ, הֻתְּרָה הָרִאשׁוֹנָה לִשְׁאָר אַחִים, שֶׁהֲרֵי הָאַחֲרוֹנָה שֶׁאָסְרָה אוֹתָהּ, חָלְצָה אוֹ נִתְיַבְּמָהּ לַמֻּתָּר לָהּ. אֲבָל אִם הָאַחֲרוֹנָה אֲסוּרָה לְאֶחָד מֵהֶם מִשּׁוּם עֶרְוָה, הֲרֵי הוּא מֻתָּר לְיַבֵּם הָרִאשׁוֹנָה, וּשְׁאָר הָאַחִים אֲסוּרִים בִּשְׁתֵּיהֶן, וְחוֹלְצוֹת וְלֹא מִתְיַבְּמוֹת:
1 A woman who is not fit to do yibbum [levirate marriage] when it falls to her because of the prohibition of sexual impropriety ["erva"], is forbidden [to remarry the brother] forever, even when the prohibition is lifted. For example, two brothers who marry two sisters, and one of the [brothers] died, and his wife falls to the second who is married to her sister. Even if his wife dies afterward [and now he would be able to marry the sister], for the prohibittion of the sister of one's wife had been lifted, even so, she is prohibited [to him]. [This is so] even if she falls to him [in yibbum] another time [even] after the death of his wife. For example, [two brothers marry two sisters, and] they have a third brother who does not have this erva [because he was not married to one of the sisters, and then one of the brothers dies], and he performs [yibbum] with her. Then, the [brother's] wife who was the sister dies. [Then,] the third [brother] who did [the yibbum] dies, and now she falls to him, she is [still] prohibited to him. It matters not if his wife had died before the third had performed [yibbum], and it matters not if she died after he had performed [yibbum]: Even though she was not prohibited to him the last time she fell to him [in yibbum], even so, she is prohibited to him, she and her secondary wives, for example when the third brother had another wife, once she was already prohibited to him the first time around. But if she was permitted to him when she [first] fell to him [in yibbum], even if she became prohibited to him afterwards, if the prohibition [eventually] lifts, the permittedness returns to her. What's the case? There are three brothers, two of whom are married to two sisters. One of them dies, so his wife is tied to yibbum with the third [brother] who is not married to her sister. He did not have a chance to perform [yibbum] with her, and the second brother dies who was married to the other sister [so now both sisters are the third brother's yibbums], but both [together] are forbidden to him. [Now,] the second [of those sisters] dies. The first becomes permitted to him again, since she was permitted to him [the first time] she fell to him in yibbum, even though in between she was prohibited to him. But if it was the first [sister] hat died, the second one would not be permitted to him, since she was prohibited to him when she fell to him in yibbum. And so if they had more brothers there, and one of them goes and performs chalitza with the second one, who is permitted to him, the first one becomes permitted to the rest of the brothers, for the second one caused her prohibition [to the brothers], and it takes chalitza or yibbum to make her permitted But if the second one was prohibited to one of them because of erva, he can perform yibbum on the first, and the rest of the brothers are prohibited to both, and they must perform chalitza and not yibbum.