“Muslims are bound by their conditions, except for a condition that permits what is unlawful or prohibits what is lawful.” (1) Likewise, he said: “Every condition that is not found in the Book of Allah is invalid, even if there are a hundred conditions.” (2)
In sum, the basic principle regarding conditions is that they are lawful and valid, whether in marriage, sale, leasing, mortgage, or endowment. The ruling on conditions stipulated in contracts, when they are valid, is that they must be fulfilled, in marriage and elsewhere, due to the general import of Allah’s saying: “O you who believe, fulfil your contracts.” For fulfilling a contract entails fulfilling both the contract itself and the conditions and specifications it contains, since all of these form part of the contract.
It has been said:
The basic rule for things is permissibility; deem worship prohibited
Unless the Lawgiver has granted permission. (3)
Strangely, the jurists of the school of law—may Allah have mercy on them—hold that fulfilling conditions in a marriage contract is recommended rather than obligatory, even for one who has no right to annul the marriage. Yet this view is weak and contrary to the view