Is it permissible, Islamically, to draw up a written declaration of an irrevocable, final divorce, along with a waiver of child custody to the mother and grandmother, in order to avoid the evil of the husband who abuses his wife, knowing that he had divorced her once and then took her back during her 'iddah? And what is the Shariah-compliant wording for this declaration to ensure the wife is not forced to return to him?

If the husband harms his wife or her parents, she is permitted to request a divorce due to harm. She may refer the matter to a judge to pronounce the divorce for him, or she may seek a khul' (divorce at the wife's instance) by renouncing some of her rights in exchange for the divorce. In these cases, the husband does not have the right to take her back (ruju'). As for the custody of the children after a khul', it belongs to the mother unless there is a legitimate impediment preventing her.