Jerusalem Talmud Yevamot 2.8

משנה: שְׁנַיִם שֶׁקִידְּשׁוּ שְׁתֵּי אֲחָיוֹת זֶה אֵינוֹ יוֹדֵעַ אֵיזוֹ קִידֵּשׁ וְזֶה אֵינוֹ יוֹדֵעַ אֵיזוֹ קִידֵּשׁ. זֶה נוֹתֵן שְׁנֵי גִיטִּין וְזֶה נוֹתֵן שְׁנֵי גִיטִּין. מֵתוּ לָזֶה אָח וְלָזֶה אָח זֶה חוֹלֵץ לִשְׁתֵּיהֶן וְזֶה חוֹלֵץ לִשְׁתֵּיהֶן. לָזֶה אֶחָד וְלָזֶה שְׁנַיִם. הַיָּחִיד חוֹלֵץ לִשְׁתֵּיהֶן וְהַשְׁנַיִים אֶחָד חוֹלֵץ וְאֶחָד מְיַיבֶּם. קָדְמוּ וְכָנְסוּ אֵין מוֹצִיאִין מִיָּדָן.

MISHNAH: If two [men] gave qiddushin to two sisters and neither of them knows to which one he gave his, each one of them gives two bills of divorce. If they died and each one had a brother, each [brother] performs ḥalîṣah with both [sisters]. If one had one [brother] but the other had two, the single one performs ḥalîṣah with both [sisters], but of the two brothers one performs ḥalîṣah and the other may marry in levirate. If both married without asking, one does not remove [the women] from them.

הלכה: שְׁנַיִם שֶׁקִידְּשׁוּ שְׁתֵּי אֲחָיוֹת כול׳. תַּנֵּי. אֶחָד יִשְׂרָאֵל וְאֶחָד כֹּהֲנִים כְּסֶדֶר הַזֶּה. הָדָא דְּאַתְּ אָמַר בְּשֶׁחָלַץ וְאַחַר כָּךְ יִיבֵּם. אֲבָל אִם יִיבֵּם בַּתְּחִילָּה אָסוּר. שֶׁמָּא יָמוּת אָחִיו וְנִמְצָא כְּבָא עַל אֲחוֹת יְבִמְתּוֹ. אָמַר רַב חִסְדָּא. הָדָא אָמְרָה הַבָּא עַל אֲחוֹת יְבִימְתּוֹ לֹא פְסָלָהּ מִן הַכְּהוּנָה. אָמַר רִבִּי יוֹסֵי בַּר בָּא. תַּנֵּי רִבִּי חִיָיה. הַבָּא עַל אֲחוֹת חֲלוּצָתוֹ לֹא פְסָלָהּ מִן הַכְּהוּנָה.

HALAKHAH: “If two [men] gave qiddushin to two sisters,” etc. It was stated: These rules apply both for Israel and for Cohanim. That is, if ḥalîṣah was performed first and the levirate afterwards. But to perform levirate first is forbidden; maybe his brother will die and it will turn out that he cohabited with the sister of his sister-in-law. Rav Ḥisda said, that means that having relations with the sister of his sister-in-law does not make her unfit for [marriage into] priesthood. Rebbi Yose bar Abba said, Rebbi Ḥiyya stated: He who cohabited with the sister of a woman for whom he had performed ḥalîṣah did not make her unfit for [marriage into] priesthood.

מֵתוּ לָזֶה אָח וְלָזֶה אָח זֶה חוֹלֵץ לִשְׁתֵּיהֶן וְזֶה חוֹלֵץ לִשְׁתֵּיהֶן. בְּכָל אָתָר אַתְּ אָמַר. אֵין חֲלִיצָה אַחַר חֲלִיצָה. וְהָכָא אָמַר אָכֵין. כָּאן בְּוַודַּאי כָּאן בְּסָפֵק. לָזֶה אֶחָד וְלָזֶה שְׁנַיִם. הַיְּחִידִי חוֹלֵץ לִשְׁתֵּיהֶן וְהַשְּׁנַיִם אֶחָד חוֹלֵץ ואֶחָד מְיַיבֶּם. בְּכָל אָתָר אַתְּ אָמַר. כָל מָקוֹם שֶׁ(אֵין) אוֹמְרִים לוֹ. יַיבֵּם. אֵין אוֹמְרִים לוֹ. חֲלוֹץ. וְהָכָא אַתְּ אָמַר אָכֵין. כָּאן בְּוַודַּאי כָּאן בְּסָפֵק. קָדְמוּ וְכָנְסוּ אֵין מוֹצִיאִין מִיָּדָן.

“If they died and each one had a brother, each [brother] performs ḥalîṣah with both [sisters]. Everywhere else you say “there cannot be ḥalîṣah after ḥalîṣah” but here you say so? There if it is certain, here one is in doubt. “If one had one [brother] but the other had two, the single one performs ḥalîṣah with both [sisters], but of the two brothers one performs ḥalîṣah and the other may marry in levirate. Everywhere else you say, in any case one asks him to perform the levirate one does not say perform ḥalîṣah; but here you say so? There if it is certain, here one is in doubt. “If both married without asking, one does not remove [the women] from them.”