"Diseases of the Soul - 4: Hypocrisy (Nifaq)" provides an in-depth analysis of the sin of hypocrisy (Nifaq) as viewed in Islamic teachings. This book examines the characteristics, causes, and consequences of hypocrisy, which is considered one of the most dangerous spiritual diseases in Islam. Through references to the Quran, Hadith, and the works of Islamic scholars, the book explains how hypocrisy undermines faith, destroys trust, and corrupts the heart. It discusses the various forms of Nifaq, from the outward display of faith without true belief to deceitful actions that contradict one’s professed values. The book also offers practical strategies for self-examination and spiritual purification to help readers avoid and overcome hypocrisy, aiming to foster sincerity, integrity, and faithfulness in one’s relationship with Allah and others.