What is the ruling on the *mahr* for a wife whose first marriage is voided after she bore a child from a subsequent man?

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In a dispute heard by Ali (may Allah be pleased with him) concerning a woman whose first husband, 'Ubayd Allah ibn al-Hurr, returned after she married 'Ikrimah and bore his child, Ali ruled that the woman was more entitled to her property than 'Ubayd Allah. She relinquished any *mahr* due from 'Ikrimah to him. After she delivered the child, she was returned to 'Ubayd Allah ibn al-Hurr, and the child was legally ascribed to its biological father, 'Ikrimah.