The du'aa' of Dhun-Nun (Yunus) by which he invoked Allah from within the belly of the whale was "There is none worthy of worship except You. You are pure. Verily I am amongst the oppressors.?" (Soorat Al-Anbiyyaa', 21:87) The Prophet, may Allah bless him and grant him peace, said about the Invocation of Yunus, 'None who is experiencing difficulty recites it except that Allah will relieve him of his difficulty."  Shaykh-ul-Islaam Ibn Taymiyyah was asked about the du'aa' of Yunus and He answers it in the form of this Book. Questions answered include: What is the meaning of this du'aa'? Are there any unstated connection between belief in the heart and the meaning of this supplication? What is the connection between belief in the heart and the meaning of this supplication such that it leads to the removal of difficulty?