What is the ruling of Islamic law regarding a mother forcing her son to divorce his wife, whom he chose for her religiousness and good character, knowing that the wife is older than him, and the mother threatens to disown her son if he does not divorce his wife?

Obeying one's mother is obligatory in what is good and permissible. However, her obedience is not obligatory if she orders her son to divorce his wife without a legitimate religious reason, and the son is not considered disobedient for not obeying in this case. Ibn Muflih mentioned in "Al-Adab Al-Shar'iyyah" that Imam Ahmad disliked a man divorcing his wife at his mother's command. Sheikh Taqiyuddin said that divorcing one's wife at the mother's request is not an act of righteousness; rather, it is impermissible. Therefore, do not divorce your wife as long as she is righteous, and strive to be dutiful to your mother and to please her, and seek help from wise people to mediate and convince her.