DISCLAIMER. This is not meant to be a fatwa on the matter. Rather, it is a collection of the opinions expressed in multiple publications. One should always seek a fatwa from a scholar knowledgeable about the topics of marriage contracts and their consequences.
A woman may include a clause in the marriage contract to be the only wife according to a good number of scholars. In other words, this is considered appropriate, albeit that there is a difference of opinions on the consequences of such a condition.
Such a condition (according to the Hanbali school):
- will not deprive the husband of his right to take additional wives,
- will not render the husband's future marriages unlawful,
- will allow the wife to exercise an annulment of the marriage contract at her own discretion which will be treated as any standard divorce (monetary compensation, custody, being able to remarry after iddah, etc.),
- will allow the wife to forfeit her right to exercise an annulment of the marriage contract and continue with her marriage as one of the wives of her husband.
There is no defined time limit as to when she can exercise her rights if annulment of the marriage contract; this has to be dealt with on a case-by-case basis through a qualified mufti.
As per Islam Q&A Fatwa 223559 (Arabic only), we as Muslims are commanded to fulfill our contracts (long as said contracts do not make what is lawful unlawful, and vice versa — see Jami' at-Tirmidhi, Vol. 3, Book 13, Hadith 1352):
يَا أَيُّهَا الَّذِينَ آمَنُوا أَوْفُوا بِالْعُقُودِ ۚ أُحِلَّتْ لَكُم بَهِيمَةُ الْأَنْعَامِ إِلَّا مَا يُتْلَىٰ عَلَيْكُمْ غَيْرَ مُحِلِّي الصَّيْدِ وَأَنتُمْ حُرُمٌ ۗ إِنَّ اللَّهَ يَحْكُمُ مَا يُرِيدُ
O you who have believed, fulfill [all] contracts. Lawful for you are the animals of grazing livestock except for that which is recited to you [in this Qur'an] - hunting not being permitted while you are in the state of ihram. Indeed, Allah ordains what He intends.
— Surat Al-Ma'idah 5:1
Hence, a condition as such in a marriage contract must be respected or the wife gets the right to annul the marriage.
Hanafi
The Hanafi view is that a woman may not add such conditions to a marriage contract. However, if such were added to a marriage contract, they are not binding while the marriage contract itself remains valid otherwise (separability of clauses). Muhammad al-Shaybani said in Al-Hujja, Vol. 3, pp. 214 that if such a condition is included in a marriage contract, it renders the contract valid, but the condition not binding.
Maliki
The Maliki view as explained by 'Illish in Fath al-'Ali al-Malik, Vol. 1, pp. 335 is that if such a condition is added to the marriage contract, there would be one of two courses:
- The intention is to annul the marriage if the condition is not fulfilled, in which case, if the husband marries again, the previous wife is automatically divorced.
- The intention is to give the wife the choice to annul or continue with the marriage.
Shafi'i
The Shafi'i school is the same as the Hanafi school. In Rawdat at-Talibīn, Vol. 7, pp. 265, An-Nawawi said if a condition in a marriage contract contradicts the norms of marriage, said condition would not be binding, let that be that the husband does not take additional wives, not to divorce her, or have right-hand possessions, or not to have her travel with him, or to divorce any of his previous wives, etc.
Hanbali
The Hanbali view is explained by Ibn Taymiyyah in Majmū' al-Fatawa Vol. 32, pp. 170 where he said that if the marriage contract stipulates that the husband should not take another wife, and he does, then the wife has the right to annul the marriage while keeping all her rights or to continue with the marriage. Ibn Qayyim al-Jawziyya shared the same view of his teacher in I'lām al-Muwaqqi'īn, Vol. 1, pp. 238-239. He added that 'Umar ibn al-Khattab, Sa'd ibn Abi Waqqas, 'Amr ibn al-'Aas, and Mu'awiya ibn Abi Sufyan all agreed that a woman may put conditions in her marriage contract related to her lodging, place of residence, and not to have additional wives. Ibn Qudamah also confirmed this in al-Mughni, Vol. 9, pp. 483.
this is the norm in Muslim society....No it is not. The terms "Muslim culture" and "Muslim society" are misnomers. While Islam does provide a basis to the cultures of Muslims, their own cultures vary from nation to nation. Polygamy is more widely accepted in Arab world than it is in let's say Turkey, Central Asia and South Asia where polygamy exists and isn't unheard of but is viewed as peculiar and rare.