What is the ruling of Islamic law regarding a person who refrains from prayer and fasting, claiming to suffer from bipolar disorder, despite being physically able to perform these acts of worship, and believing that God will forgive him because he is ill, while also engaging in backbiting and slander?

Prayer is obligatory upon a person as long as their intellect is present, and it is not waived due to illness or organ damage; because the basis of accountability is puberty and intellect. If the mental illness does not impair the intellect, then the patient is obligated to pray and fast. If they become insane and then recover, they are excused during the period of their intellectual absence, and they must make up what they missed when they recover. It is necessary to advise them and remind them of the great importance of prayer and fasting, for being far from the remembrance of Allah is one of the causes of mental illnesses, and His remembrance reassures hearts. A person is responsible for their actions as long as they are aware, and their illness is not an excuse for committing sins.