Jerusalem Talmud Yevamot 1.5

משנה: שֵׁשׁ עֲרָיוֹת חֲמוּרוֹת מֵאֵילּוּ מִפְּנֵי שֶׁנְּשׂוּאוֹת לָאֲחֵרִים צָרוֹתֵיהֶן מוּתָּרוֹת. אִמּוֹ וְאֵשֶׁת אָבִיו וָאֲחוֹת אָבִיו אֲחוֹתוֹ מֵאָבִיו. וְאֵשֶׁת אֲחִי אָבִיו וְאֵשֶׁת אָחִיו מֵאָבִיו.

MISHNAH: Six incest prohibitions are more stringent than these since they [concern women who] must be married to others, their co-wives are permitted: A man’s mother, his father’s wife, his father’s sister, his paternal sister, his paternal aunt, and his paternal brother’s wife.

הלכה: שֵׁשׁ עֲרָיוֹת חֲמוּרוֹת מֵאֵילּוּ מִפְּנֵי שֶׁהֵן נְשׂוּאוֹת לָאֲחֵרִים כול׳. מַה אִינָּה חֲמוּרָה. הָכָא כָרֵת וְהָכָא כָרֵת. הָכָא מַמְזֵר וְהָכָא מַמְזֵר. מַהוּ חֲמוּרוֹת. שֶׁאֵינָן יְכוֹלוֹת לְהִינָּשֶׂא לָאַחִים שֶׁלֹּא בַעֲבֵירָה. וְתַנֵּי רִבִּי חִיָיה כֵן. וְכוּלָּן אִם יְכוֹלוֹת לְהִינָּשֶׂא לָאַחִין שֶׁלֹּא בַעֲבֵירָה צָרוֹתֵיהֶן פְּטוּרוֹת מִן הַחֲלִיצָה וּמַן הַיִּבּוּם.

HALAKHAH: “Six incest prohibitions are more stringent than these since they [concern women who] must be married to others”, etc. In what are they more stringent? Here there is extirpation, there is extirpation. Here there is bastardy, there there is bastardy. What is more stringent? That they cannot be married to the brothers without transgression. And Rebbi Ḥiyya stated thus: For all women who may be married to the brothers without transgression, their co-wives are free from ḥalîṣah and levirate.

תַּנֵּי רִבִּי חִיָיה. אֵין צָרָה אֶלָּא מֵאָח בִּלְבַד. אָמַר רִבִּי יוֹסֵי. מַתְנִיתָא אָמְרָה כֵן. מִפְּנֵי שֶׁהֵן נְשׂוּאוֹת לָאֲחֵרִים צָרוֹתֵיהֶן מוּתָּרוֹת. רִבִּי יִרְמְיָה בָּעֵי. וּתְהֵא צָרָה מִן הַשּׁוּק. אָמַר רִבִּי יוֹסֵה. לֹא שְׁמִיעַ רִבִּי יִרְמְיָה הָדָא דְתַנֵּי רִבִּי חִיָיה. לֹא שְׁמִיעַ לְמַתְנִיתִין מִפְּנֵי שֶׁהֵן נְשׂוּאוֹת לַאֲחֵרִים צָרוֹתֵיהֶן מוּתָּרוֹת. חָזַר וָמַר. אִין דִּשְׁמִיעַ. אֶלָּא כְּאִינַשׁ דִשְׁמִיעַ מִילָּה וּמַקְשֵׁי עֲלָהּ.

Rebbi Ḥiyya stated: “A co-wife is only from a brother”. Rebbi Yose said, our Mishnah says the same: “Since they must be married to others, their co-wives are permitted.” Rebbi Jeremiah asked: Why can there not be a co-wife from the market place? Rebbi Yose said, did Rebbi Jeremiah not hear what Rebbi Ḥiyya said, did he not hear our Mishnah, “since they must be married to others, their co-wives are permitted”? He turned around and said, certainly did he hear. But he is a person who hears something and questions it.

רִבִּי יִרְמְיָה בָּעֵי. הַבָּא עַל הַצָּרָה מַהוּ שֶׁיְּהֵא חַיָיב עָלֶיהָ מִשּׁוּם אֵשֶׁת אַח. אָמַר רִבִּי יוֹסֵי. אִילּוּ אֶיפְשַׁר לְצָרָה בְּלֹא אֵשֶׁת אַח יְאוּת. אֶיפְשַׁר לְאֵשֶׁת אַח בְּלֹא צָרָה. אֵיפְשַׁר לְצָרָה בְּלֹא אֵשֶׁת אַח.

Rebbi Jeremiah asked: If one has intercourse with a co-wife, is he guilty because of his brother’s wife? Rebbi Yose said, if a co-wife were possible without a brother’s wife, that would be a valid question. It is possible to be a brother’s wife without a co-wife. It is impossible to be a co-wife without a brother’s wife.

וְאֵשֶׁת אָח לֹא יְבִמְתּוֹ הִיא. אָמַר רִבִּי יוֹסֵה בֵּירִבִּי בּוּן. תִּיפְתָּר שֶׁהָיָה לָהּ בָּנִים מֵאַחִים.

Is the brother’s wife not his sister-in-law? Rebbi Yose bar Abun said, explain it if she had children from a brother.