Is the marriage contract considered null and void if, six months later, the husband discovers that the wife's birth certificate presented to him was forged, and that she is three years older than him, contrary to their agreement? And if the contract is not null and void, what is her legitimate right if he divorces her due to the age difference?

The aforementioned marriage is valid. The husband has the option [to proceed or annul] if he stipulated that she should not be older than him, and it turned out to be otherwise. The husband has the option between upholding the marriage or annulling it. If he annuls it after consummation, she is entitled to a dowry equivalent to that of women of her status (mahr al-mithl). The husband can claim back from her guardian, who deceived him, any amount by which the designated dowry (al-musamma) exceeded the mahr al-mithl. If the mahr al-mithl exceeds the designated dowry, she is only entitled to the designated dowry. If this condition (regarding age) is considered significant in common custom, then the husband has the right to choose [to proceed or annul] unless he has done something that indicates his consent.