The Messenger of Allah said that the heart is a piece of flesh within the human body that can rectify the deeds of the entire body if it itself is rectified. However, if it is spoiled, the actions of the body will only result in sin. Elsewhere, the Messenger of Allah said:
Indeed Allah does not look at your appearance and your wealth but He looks to your heart and your actions
Hence, the state of the heart determines if actions will be righteous or sinful, and therefore determines a person’s spiritual status. Allah says in the Holy Quran:
Allah has not made for any man two hearts in one body [33:4]
Two hearts cannot coexist within the same body in such a manner that one heart is dedicated to Allah and the other to Shaitan. There is only one heart that can only be devoted to one. Man should focus on keeping the heart fragrant with the remembrance of Allah.