What is the validity of a wife's promise to pay a debt after the husband pronounces divorce with the debt mentioned?

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If the wife responds by saying, 'I guarantee you a thousand,' the statement is invalid. Guarantee (dhaman) is only applicable for an existing obligation upon the guaranteed party or one that will inevitably become an obligation, neither of which applies here. However, it is narrated that Al-Qadi deems it valid because guaranteeing an obligation that has not yet materialized is permissible. This validity is understood only if the wife had promised the amount before the divorce pronouncement, contingent upon him divorcing her; in such a case, if he says, 'You are divorced, and you owe me a thousand,' he is entitled to the thousand.