He found out after marriage that his wife is mentally ill. Should he ask for the mahr to be returned?

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Check below answers in case you are looking for other related questions:
Is it permissible to give zakaah to a poor girl to cover the expenses of her wedding?
He gave his wife her mahr: a ring that he bought with riba

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The negative and harmful consequences of exaggerating concerning the dowry
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He divorced her in return for half of the mahr after he accused her. Does he have the right to this money?
Is it permissible to give zakaah to a poor girl to cover the expenses of her wedding?
He gave his wife her mahr: a ring that he bought with riba

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