What is the ruling on a wife withholding herself from her husband who does not provide for her and their children, while he provides for his other wife?

A husband must be just among his wives, and the wife's maintenance is obligatory upon her husband. If the husband withholds the obligatory maintenance, the wife should remind him of Allah and of her rights and the rights of his children. If he does not respond, she is permitted to refer the matter to the judiciary.

However, if the husband fulfills the obligatory maintenance but favors the other wife with gifts and presents, the wife is not permitted to refuse intimacy with him, because he is not obligated to be just in these matters.