In some cases, either spouse can add conditions to a marriage contract, but depending on their nature, they may be valid or invalid.
Conditions relating to rights
If the contract emphasises rights ordained by the Sharia, e.g. the wife shall receive financial support, clothing and shelter or the wife will be obedient to the husband in everything permissible that is related to their marriage, or regular sexual intercourse, etc, then the ruling for such conditions is that, it is necessary for both spouses to fulfil them, even if they are not stipulated in the contract. If the husband fails to act in accordance with such rights, the wife has a right to demand for a legal divorce in an Islamic court. This is regardless of it being in the contract or not (Radd al-Muhtar, 2/45).
Conditions opposing rights
If the contract stipulates conditions against what is ordained by the Sharia, e.g. the wife will not receive her dowry, financial support, or the condition that the husband will not have the right to have sexual intercourse, or that he will divorce his first wife, etc, then the rulings for such conditions is that they will be void but the marriage will still be valid. It will be as tough they have got married without those conditions. Neither will any of the spouses be obliged to fulfil them.
General conditions
If the contract stipulates general preferential conditions like the husband may not marry again or the husband cannot force the wife to leave her home town, or the wife will be the primary homemaker, etc, then, the Hanbalis say, it is necessary to fulfil these conditions, and if the husband is negligent in any way, the wife will have the right to demand nullification of the marriage. However, according Hanafis, Shafi’i’s and Malikis, it is a religious duty of the husband to fulfil these conditions, but it is not binding on him legally in so far as it is not something that can be enforced through the courts, and the wife can not demand to nullify the marriage. So if the husband decides to marry again, then it will be lawful for him, however, it is the moral responsibility of the husband to fulfil his promise.
The Messenger of Allah (Allah bless him & give him peace) regarded not fulfilling of promises as “the sign of a hypocrite”, thus a person will be sinful for not fulfilling these conditions, but it will not have an effect on the marriage.
Conditions relating to Talaq e Tafweed
Talaq e Tafweed is where a man delegates one of his rights of divorce to his wife. She will be able to take this right and divorce herself. There are many rules about Talaq e Tafweed. A woman may also demand this right from her husband but the rules differ on when she does so.
The first situation is before the actual marriage takes place the woman stipulates that if certain conditions are not fulfilled, she will have a right to divorce herself. If the husband acknowledges and agrees then this is permissible.
The second situation is at the time of marriage, the wife stipulates the conditions and demands the right to divorce herself in the case of non-fulfilment. This is also permissible but will only be valid if the woman initiates the offer of marriage along with the right of divorce, e.g. “I want to marry you on the condition that you give me an allowance of £250 per month and if you do not then I will have the right to divorce you.” and the man accepts this condition. As she is gaining the right of divorce, then it is incumbent for her to initiate it and not for the man. If she does not initiate the marriage or the man does not accept the condition then it will be void.
The third situation is after being married, in this case, either the husband can give his wife the right to divorce or she can request it from him. If he gives her the right, he can also place conditions around it like ‘only in this instance’ or ‘for the next 3 years.’