Quote  Category: Qur'an “What is Faith? When your good deed pleases you and your evil deed grieves you, you are a believer. What is Sin? When a thing disturbs (the peace of) your heart, give it up.” - Prophet Muhammad (570-632) Sayings of Muhammad. by Prof. Ghazi Ahmad - Arabian, b. Mecca, son of Abdallah, descended of Ishmael. Email this quote to a friend! If there is an error in this quote please let us know. Famous Quotes © ® All rights reserved.