Jerusalem Talmud Gittin 9.5

משנה: שְׁנַיִם שֶׁשִּׁילְּחוּ שְׁנֵי גִיטִּין שָׁוִין וְנִתְעָרְבוּ נוֹתֵן שְׁנֵיהֶן לְזוֹ וּשְׁנֵיהֶן לְזוֹ. לְפִיכָךְ אִם אָבַד אֶחָד מֵהֶן הֲרֵי הַשֵּׁינִי בָטֵל.

MISHNAH: If two men sent two identical bills of divorce which became mixed up, one delivers both to both women. Therefore, if one of them was lost, the second became unusable.

הלכה: שְׁנַיִם שֶׁשִּׁילְּחוּ שְׁנֵי גִיטִּין שָׁוִין כול׳. רִבִּי אֶלְעָזָר בֵּירִבִּי יוֹסֵי בְּעָא קוֹמֵי רִבִּי יוֹסֵי. כְּמַה דְאַתְּ אֲמַר. גֵּט אַחַר גֵּט פָּסוּל בִּשְׁתֵּי נָשִׁים. וְדִכְוָותָהּ וְהוּא שְׁנֵי גִיטִּין פְּסוּלִין בִּשְׁתֵּי נָשִׁים. אָמַר לֵיהּ. וְכֵינִי. אָמַר לֵיהּ. וְהָא תַנִינָן. שְׁנַיִם שֶׁשִּׁילְּחוּ שְׁנֵי גִיטִּין שָׁוִין וְנִתְעָרְבוּ נוֹתֵן שְׁנֵיהֶן לְזוֹ וּשְׁנֵיהֶן לְזוֹ. תַּמָּן זֶה כְּרוּת לִשְׁמָהּ וְזֶה כְּרוּת לִשְׁמָהּ. תַּעֲרוֹבֶת הִיא שֶׁגָּרְמָה. בְּרַם הָכָא לֹא זֶה כְּרוּת לִשְׁמָהּ וְלֹא זֶה כְּרוּת לִשְׁמָהּ. מִכֵּיוָן שֶׁנְּתָנוֹ לָהּ יֵעָשֶׂה כְּמִי שֶׁכְּרוּת לִשְׁמָהּ מִשָּׁעָה רִאשׁוֹנָה.

HALAKHAH: “If two men sent two identical bills of divorce,” etc. Rebbi Eleazar ben Rebbi Yose asked before Rebbi Yose: Just as you say that a bill of divorce after a bill of divorce is invalid in the case of two wives, similarly two bills of divorce should be invalid for two women. He answered, that is correct. He said to him, but did we not state: “If two men sent two identical bills of divorce and they became mixed up, one delivers both to both women”? There, each of the bills was written in the name of the respective wife; the mix-up caused the problem. But here, neither one was written as divorce in her name; when it was delivered, could it be considered as divorce in her name from the start?