This book presents over 160 proofs for the Sunni understanding of Sunna and bid'a as it was set forth in classical, moderate, mainstream Islam according to the Sunni Salaf and Khalaf, including the four schools of fiqh. It includes case studies on topics such as collective supplication, partitions for women in mosques, and proofs for visitation of the grave by women. The author, Dr. Gibril Fouad Haddad, is a Lebanese-born Islamic scholar, hadith expert, author, and translator of classical Islamic texts. The main purpose of this book is to provide a comprehensive understanding of Sunna and bid'a as it was set forth in classical, moderate, mainstream Islam according to the Sunni Salaf and Khalaf. It includes over 160 proofs to support this understanding and provides case studies on various topics such as collective supplication, partitions for women in mosques, and proofs for visitation of the grave by women. The author, Dr. Gibril Fouad Haddad, is a renowned Lebanese-born Islamic scholar, hadith expert, author, and translator of classical Islamic texts. His work is highly regarded in the Muslim world and he is considered one of the clearest voices of traditional Islam in the West.