All praise and thanks are due to Allah for helping me in preparing this book. In the process of writing the various parts of this book, many brothers contributed with their suggestions and modifications as well as encouragement. The people in charge of Radio Riyadh (English Service) offered moral support to prepare the various chapters that were broadcast in the form of radio episodes. Then there was the encouragement I received from the publisher of the first version of the book. This second edition was not possible without the support of Darussalam and its able Director