Is it permissible to take the increase in the deferred mahr, handwritten by the husband and not officially documented, to compensate for the doubling in the price of gold?

A will in favor of an heir is not permissible unless the other heirs approve it, due to the saying of the Messenger of Allah, peace and blessings be upon him: "There is no will for an heir," and "A will for an heir is not permissible unless the heirs wish it."

The deferred dowry is a right of the wife and a debt upon the husband, to be paid from his estate before its distribution. If the currency value decreases, the debt is to be estimated based on the value of gold at the time the debt was established, or through reconciliation to distribute the harm between the two parties. The wife is not permitted to receive more than that, unless the heirs ratify the husband's will.