What is the ruling if a seriously ill man marries a woman and grants her a dowry exceeding her due (Mahr al-Mithl), and then dies?

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If a seriously ill man marries a woman and assigns her a dowry that is greater than her due dowry (Mahr al-Mithl), and he does not possess anything else, and then he dies and his heirs inherit, the excess portion of the dowry (the gratuity or favor, Mahabah) is invalidated. This is because it constitutes a bequest (Wasiyyah) in favor of an heir. She receives her due dowry, and one-quarter of the remainder is hers through inheritance.