Does divorce take effect if the husband swore an oath of triple divorce upon his wife for her to return money she had taken without his knowledge, and she only returned a portion of it? And is an expiation required of him for this oath?

It is not permissible for a wife to take her husband's money without his permission unless he restricts her and does not provide her with adequate sustenance according to what is customary. Regarding the husband swearing to divorce his wife if she does not return the money: if he intended for all the money to be returned, then she must return it to avoid him breaking his oath and the divorce taking place, according to the majority of scholars. However, according to the view of Sheikh Al-Islam Ibn Taymiyyah, an expiation for breaking an oath (kaffarat yameen) is due. If he did not intend for all the money to be returned, then breaking the oath does not occur if she returns most of it. If there was no specific intention, then she must return all the money to avoid divorce, even if it means taking a loan.