אבן העזר ט׳Even HaEzer 9

Se’if 1א׳

אִשָּׁה שֶׁנִּשֵּׂאת אוֹ נִתְאָרְסָה (מ"מ פכ"א וְנ"י פ' הַבָּא עַל יְבִמְתּוֹ) לִשְׁנֵי אֲנָשִׁים, וּמֵתוּ, לֹא תִּנָּשֵׂא לִשְׁלִישִׁי, שֶׁכְּבָר הֻחְזְקָה לִהְיוֹת אֲנָשֶׁיהָ מֵתִים. וְאִם נִשֵּׂאת לֹא תֵּצֵא, וַאֲפִלּוּ נִתְקַדְּשָׁה יִכְנֹס. וְאִם הִכִּיר בָּהּ, יֵשׁ לָהּ כְּתֻבָּה; לֹא הִכִּיר בָּהּ, אֵין לָהּ כְּתֻבָּה מִשְּׁלִישִׁי, אֲבָל מִשֵּׁנִי יֵשׁ לָהּ כְּתֻבָּה, אֲפִלּוּ לֹא הִכִּיר בָּהּ. הַגָּה: יֵשׁ אוֹמְרִים דְּדַוְקָא אִם מֵתוּ מִיתַת עַצְמָם, אֲבָל אִם נֶהֱרַג אֶחָד מֵהֶן אוֹ מֵת בְּדֶבֶר, אוֹ נָפַל וָמֵת וְכַדּוֹמֶה, אֵינוֹ כְּלוּם. וְלָכֵן רַבִּים מְקִלִּים בִּדְבָרִים אֵלּוּ, וְאֵין מוֹחִין בִּידֵיהֶם (ב"י בְּשֵׁם תְּשׁוּבַת הָרַמְבַּ"ן סי' קכ"א שֶׁכ"כ בשי"א). יֵשׁ אוֹמְרִים דְּהוּא הַדִּין אִשָּׁה שֶׁנִּתְגָּרְשָׁה שְׁנֵי פְּעָמִים, אֵין לִשָּׂא אוֹתָהּ (רַשִׁ"י פ"י דִּיבָמוֹת וְהָרַ"ן ר"פ נַעֲרָה). אֲבָל יֵשׁ אוֹמְרִים מִיתָה דַּוְקָא (הַגָּהַת מַיְמוֹנִי בְּשֵׁם התוס'), וְכֵן עִקָּר:

A woman who was married (Rem"a: or engaged) (Maggid Mishneh ch. 21 and Nimmukei Yosef ch. Haba `Al Yevimto) to two men [sequentially] and they died may not become married to a third, for she is already assumed to be [a woman whose] husbands die. But if she married [a third husband] she need not get divorced, and even if she was [only] engaged, he may marry [her]. And if he is aware of her [as a woman whose husbands die, and nevertheless consents to marry her] she receives a ketubah; [but] if he is unaware of her [past], she gets not ketubah from the third. But from the second [husband whom she married after the first died] she has a ketubah even [if] he was unaware of her. Rem"a: There are those who say that [this law applies] specifically if they died natural deaths, but if one of them was murdered or died in a plague, or fell and died, etc., that doesn't count. And therefore most people are lenient in these matters, and one ought not prevent them [from acting leniently]. (Beit Yosef in the name of a responsum of the Ramban 121, who wrote this in the name of "those who say.") There are those who say that this law applies to a woman who is divorced twice, that one ought not marry her. (Rashi, ch. 10 of Yevamot and the Ra"n in the beginning of ch. Na`arah.) But there are those who say that [this law applies] specifically to dying (Hagahat Maimoni in the name of the Tosafot), and thus is the norm.

Se’if 2ב׳

אִישׁ שֶׁמֵּתוּ שְׁתֵּי נָשָׁיו, אֵינוֹ מוֹנֵעַ עַצְמוֹ מִלִּשָּׂא:

A man whose two wives die may not prevent himself from marrying a third