Tractate Yevamot - Chapter 14 - Mishnah 9

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? He must marry her, but if he wishes to divorce her he may do so. 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? He must marry her and he may never divorce her.