What is the ruling on a husband asking his wife to waive part or all of her deferred dower (Mahr Mu'akhkhar) if he intends to divorce her and she is unaware of his intention? And is it permissible to pay the deferred dower in installments if a divorce occurs?

If a mature and sane wife willingly waives her deferred Mahr (dowry) or a portion of it, her waiver is valid. However, if the waiver was due to her desire for the marriage to continue, and then the husband divorced her, she has the right to revoke this waiver. If the husband is unable to pay the deferred Mahr in one lump sum after the divorce, he must be granted a respite and allowed to pay in installments according to his financial capacity, unless he is capable of paying, in which case installments are not permissible except with the wife's consent.