What is the ruling of Islamic law regarding the inheritance of a son who was not dutiful to his deceased mother, and is it permissible to withhold his share or to donate the gold owned by the mother to the poor?

What the son did is an act of disobedience (Uquq) and a major sin. He must repent and strive to honor his mother after her death. It is not permissible to disinherit a disobedient son, because a child inherits from his father and mother by lineage, not by righteousness. The impediments to inheritance are: slavery, murder, and difference of religion, and disobedience is not among them. He must be enabled to take his rightful share, informed about the inheritance, and nothing should be concealed from him. It is not permissible to distribute his share to the needy without his permission and consent.