Is it permissible for a father to be unjust in his dealings with his adult children, and to see his son in debt and in a bad financial situation and not help him despite possessing wealth, and if not permissible, what is his punishment?

If the lack of justice among children is concerning gifts, refer to fatwas: 32485, 32848, 45195. If it is concerning treatment, refer to fatwa: 39775. A father is not obligated to spend on an adult son unless the son is unable to provide for himself. However, if he does so, he will receive a great reward. It is obligatory for the son to honor his father, obey him, and be kind to him, regardless of the father's treatment. This should not be an excuse for disobedience or ill-treatment.