Is it permissible to agree, during the marriage contract, that the marriage shall expire upon the death of one of the parties, thereby nullifying inheritance and claims resulting from the marriage, especially if the marriage is clandestine?

Marriage effectively ends with the death of one of the spouses, though some of its effects remain, such as inheritance and the waiting period (iddah). The spouses do not have the right to waive these at the time of the contract. Therefore, waiving inheritance is not valid until it becomes due upon death, and waiving the iddah is not permissible because it is a right of Allah Almighty. As for other rights that can be temporarily waived, such as sexual enjoyment and service, waiving them is permissible. However, if the husband demands his right, the wife is obliged to fulfill it. The wife can waive rights such as maintenance (nafaqah), housing (sukna), and the equitable division of nights for cohabitation (qasm fil-mabeet).