Is raising one's voice at a sick father who refuses to take his medicine or wishes for death considered an act of disobedience (ʿuqūq) and a major sin (kabīrah) warranting entry into Hellfire, especially given attempts to apologize to him and generally show him kindness, or does disobedience (ʿuqūq) have degrees, and not every act that displeases the parent is a major sin?

It is not permissible to chide one's father, raise one's voice at him, speak harshly to him, or show annoyance in his face, even if it is for his own benefit, such as receiving medical treatment. This is based on the Almighty's saying: "So do not say to them [even] 'uff,' and do not repel them." The criterion for forbidden disobedience is every word or action that causes significant harm to the father, except in cases of polytheism or disobedience [to Allah], or if the father's command results from foolishness or stubbornness. Therefore, one must be gentle with the father in persuading him to take medicine, and if he insists on not taking it, there should be no reprimand or violence, for medical treatment is not obligatory.