Yevamot, Chapter Fourteen, Mishnah Nine
This is the final mishnah of the chapter and it concludes the rather long series of mishnayot which we have seen throughout the entire chapter.
1) If two brothers, one of whom was deaf and the other of sound senses, were married to two strangers, one of whom was deaf and the other of sound senses, and the deaf brother, the husband of the deaf woman, died, what should the brother of sound senses, the husband of the woman of sound senses do?
a) He must marry her, but if he wishes to divorce her he may do so.
2) If the brother of sound senses, the husband of the woman of sound senses, died, what should the deaf brother, the husband of the deaf woman, do?
a) He must marry her and he may never divorce her.
Section one: When the deaf brother, married to the deaf woman dies, she becomes liable for yibbum or halitzah with the brother of sound senses. She cannot have halitzah, because she is deaf. He must, therefore, have yibbum with her, but may afterwards divorce her, because deaf women can be divorced.
Section two: If the brother of sound senses dies, his wife of sound senses becomes liable for yibbum with the deaf brother. He cannot have halitzah because he is deaf. He must therefore marry her. He cannot subsequently divorce her because his ties to her are deoraita (due to the deoraita nature of her previous marriage), whereas his ability to divorce is only derabbanan.