The Disease and the Cure

Ad-Da’ wad-Dawaa’ (The Disease and the Cure) by Imaam Ibn al-Qayyim. He wrote it in reply to a man who was severely afflicted and feared for his life in this world and the Hereafter. Ibn al-Qayyim describes the diseases of the heart, sins, doubts and desires, and gives the cure: repentance, sincerity and turning back to Allaah. A good fit if you want to purify your heart.