Why is a woman required to return the dowry to the man when she seeks separation due to his ill-treatment, while the man is not required to pay compensation when he divorces a righteous wife, citing the story of Thabit, which differs in that there is no fault on the husband's part?

The rules of Sharia necessitate separating the spouses without compensation from the wife if the harm originates from the husband and he cannot be deterred except by separation, based on the saying of the Prophet (peace be upon him): "There should be no harm nor reciprocating harm," and Allah’s saying: "Then [there is either] retention with المعروف (kindness) or dismissal with إحسان (good treatment)." So, whoever treats his wife badly is not retaining her with ma'ruf, nor is he dismissing her with ihsan if he dismisses her for compensation. The mahr (dowry) that the wife received is hers, and she is not required to return it. The majority of scholars hold that the two arbitrators (appointed by the judge) may divorce the wife without khul' if the husband mistreats her, and khul' is valid if the wife is the one who mistreats. The Hanafis did not permit the husband to take money in this case, and if he forces her into khul', the contract is valid and the compensation is binding, but he is sinful. Therefore, it is not permissible for the judge to compel the woman to return the money to the man if she wishes to separate due to his bad treatment.