Would a divorce be considered an irrevocable major divorce if the husband wrote to his wife, "You are divorced," and then a month later wrote to her, "You are divorced, you are divorced, you are divorced," intending divorce due to problems, and then the wife returned and lived with him for four months? Is it permissible for her to remain with him in the same house, and would sexual intimacy between them be considered adultery in this case?

If you intended, by repeating "you are divorced," to confirm one or two divorces, then the divorce occurs according to your intention, and you may take her back during her 'iddah (waiting period). However, if you intended three divorces, then she is irrevocably divorced from you and is not lawful for you until she marries another man. Sexual intercourse after an irrevocable divorce (baynunah) is consideredzina (fornication/adultery) and necessitates immediate repentance and separation. Both parties must repent and adhere to the limits set by Allah.