135 Yevamot 2/7-9

(ז) שְׁנַיִם שֶׁקִּדְּשׁוּ שְׁתֵּי אֲחָיוֹת, זֶה אֵינוֹ יוֹדֵעַ אֵיזוֹ קִדֵּשׁ, וְזֶה אֵינוֹ יוֹדֵעַ אֵיזוֹ קִדֵּשׁ, זֶה נוֹתֵן שְׁנֵי גִטִּין, וְזֶה נוֹתֵן שְׁנֵי גִטִּין. מֵתוּ, לָזֶה אָח, וְלָזֶה אָח, זֶה חוֹלֵץ לִשְׁתֵּיהֶן, וְזֶה חוֹלֵץ לִשְׁתֵּיהֶן. לָזֶה אֶחָד וְלָזֶה שְׁנַיִם, הַיָּחִיד חוֹלֵץ לִשְׁתֵּיהֶן, וְהַשְּׁנַיִם, אֶחָד חוֹלֵץ וְאֶחָד מְיַבֵּם, קָדְמוּ וְכָנְסוּ, אֵין מוֹצִיאִין מִיָּדָם. לָזֶה שְׁנַיִם וְלָזֶה שְׁנַיִם, אָחִיו שֶׁל זֶה חוֹלֵץ לְאַחַת, וְאָחִיו שֶׁל זֶה חוֹלֵץ לְאַחַת, אָחִיו שֶׁל זֶה מְיַבֵּם חֲלוּצָתוֹ שֶׁל זֶה, וְאָחִיו שֶׁל זֶה מְיַבֵּם חֲלוּצָתוֹ שֶׁל זֶה. קָדְמוּ שְׁנַיִם וְחָלְצוּ, לֹא יְיַבְּמוּ הַשְּׁנַיִם, אֶלָּא אֶחָד חוֹלֵץ וְאֶחָד מְיַבֵּם. קָדְמוּ וְכָנְסוּ, אֵין מוֹצִיאִין מִיָּדָם:

(ח) מִצְוָה בַגָּדוֹל לְיַבֵּם. וְאִם קָדַם הַקָּטָן, זָכָה. הַנִּטְעָן עַל הַשִּׁפְחָה וְנִשְׁתַּחְרְרָה, אוֹ עַל הַנָּכְרִית וְנִתְגַּיְּרָה, הֲרֵי זֶה לֹא יִכְנוֹס. וְאִם כָּנַס אֵין מוֹצִיאִין מִיָּדוֹ. הַנִּטְעָן עַל אֵשֶׁת אִישׁ, וְהוֹצִיאוּהָ מִתַּחַת יָדוֹ, אַף עַל פִּי שֶׁכָּנַס, יוֹצִיא:

(ט) הַמֵּבִיא גֵט מִמְּדִינַת הַיָּם, וְאָמַר בְּפָנַי נִכְתַּב וּבְפָנַי נֶחְתַּם, לֹא יִשָּׂא אֶת אִשְׁתּוֹ. מֵת, הֲרַגְתִּיו, הֲרַגְנוּהוּ, לֹא יִשָּׂא אֶת אִשְׁתּוֹ. רַבִּי יְהוּדָה אוֹמֵר, הֲרַגְתִּיו, לֹא תִנָּשֵׂא אִשְׁתּוֹ. הֲרַגְנוּהוּ, תִּנָּשֵׂא אִשְׁתּוֹ:

(7) [If] two men betrothed two sisters and this one [one of them] does not know which he betrothed, and this one [the other] does not know which one he betrothed, this one gives two bills of divorce [one to each woman] and this one gives two bills of divorce. If they [the men] died and this one had a brother and this one had a brother, this one undergoes Chalitzah from both women, and this one undergoes Chalitzah from both women. If one of [the men] had one [brother], and the other had two [brothers] the lone bother undergoes Chalitzah from both women; and [with regard] to the two - one undergoes Chalitzah [from one woman] and one performs Yibum [with the other woman]. [If] they went ahead and married the sisters they [the women] are not removed from them. [If] this one had two [brothers] and this one had two [brothers], the brother of this one undergoes Chalitzah from one woman and the brother of this one [the other man] undergoes Chalitzah from one woman. The brother of this one performs Yibum with the Chalutzah of this one, and the brother of this one [the other man] performs Yibum with the Chalutzah of this one. [If] the two [brothers of one man] went ahead and underwent Chalitzah the two [brothers of the other man] should not perform Yibum, rather one of them undergoes Chalitzah and one of them performs Yibum. If they [the brothers of the second man] went ahead and married them [following the Chalitzah of the two] they are not removed from them.

(8) It is the obligation for the eldest brother to perform Yibum; however, if the younger [brother] went ahead [and did it] he has merited [the Mitzvah]. [If] one was accused of [having relations] with a bondwoman and she was [subsequently] freed, or with a gentile woman and she [subsequently] converted, he may not marry her. But if he did she is not removed from him. [If] one was accused of [having relations] with a married woman, and [consequently] she is removed from him [her husband], even if he [the suspected adulterer] marries [her], he must divorce [her].

(9) [If] a person brings a bill of divorce from overseas and states, "It was written before me and it was signed before me", he [the messenger] may not marry his wife [the woman named in the divorce]. [If a person testified that a man is] "dead", or "I killed him", or "we killed him", he may not marry his wife [the woman he is addressing]. Rabbi Yehudah says: [If he says] "I killed him" he may not marry his wife; [but if he says] "we killed him" he may marry his wife.