1,810. If a Woman With an Invalid Get Remarried

Hilchos Geirushin 10:4

The Sages enacted that when a woman who was given an invalid get remarries, she must be divorced by her second husband so that people shouldn’t think that a married woman was permitted to remarry without first receiving a get. She must be given a valid get from her first husband in order to then marry anyone else. A woman in this scenario is prohibited to both the first and the second husband; this is so even if she married husband #2 completely unaware of the prohibition. This is out of concern that people will think that a man remarried his divorcee after she married someone else (which is a Torah prohibition). If one of the men violated the law and remarried her, he is compelled to divorce her again.

Hilchos Geirushin 10:5

The same rule applies if a woman remarries after witnesses testify that her husband has died but he subsequently turns up alive. This is true regardless of whether the husband has all of his faculties or is congenitally deaf, and regardless of whether she remarried to a man who has all of his faculties or is congenitally deaf. The reason this distinction is made is because a man with congenital deafness doesn’t fully effect marriage. The woman must be divorced by both husbands; each giving her a get, and she is prohibited to both of them forever.