Is it permissible for a Muslim to sell cigarettes in a shop he co-owns with his father, knowing that his father disapproves of it, and should he leave home or disobey his father, given that his mother is ill and could be harmed by a dispute?

Smoking is forbidden (haram), and it is not permissible to sell it. It is not permissible to obey one's father if he orders its sale, due to the Prophet's (peace be upon him) saying: "There is no obedience in disobedience to Allah; obedience is only in what is good (ma'ruf)." One should advise him and supplicate for him, while observing proper etiquette in enjoining what is right and forbidding what is wrong. If the father insists on the son selling tobacco, then it is not permissible to obey him. The son should seek another job while striving to earn his father's pleasure. It is permissible for an adult, mature son to live independently from his parents. Benefiting from the wealth of someone whose money is mixed with both lawful and unlawful elements is disliked (makrooh), but not forbidden (haram).