What is the ruling on a father who is harsh with his wife, quarrels with her, scolds her when she is ill, and withholds her rights from her, not even giving her a kind word?

Islamic law has enjoined kindness and gentleness towards women and warned against oppressing them, for the Prophet, peace and blessings be upon him, said: "Treat women kindly," and "O Allah, I declare inviolable the rights of the two weak ones: the orphan and the woman." If the father is oppressing the mother, it is incumbent upon the children to advise him gently and respectfully and to explain to him the ruling of Islamic law, while still showing filial piety towards him no matter how badly he behaves.