What is the ruling concerning a father who prays only a little and has an intense love for money? Is his money lawful, and is it obligatory to try and advise him despite his extreme short temper and stubbornness?

The best way to advise a father who has abandoned prayer and uses foul language is through: honoring him and being kind to him, seizing appropriate opportunities, seeking help from those who influence him, avoiding embarrassing him or hurting his feelings, and sincerely supplicating for him. A father should not be advised when he is angry, and a father is not like a stranger when it comes to giving advice. As for eating from his money, if it is entirely unlawful, then it is impermissible. If lawful and unlawful money are mixed, it is permissible with disfavor if there is no necessity. If it is lawful, then it is permissible without disfavor.