This book is considered one of the most important books of Shafi'i, as it has collected the modern evidence of the doctrine as a way out of the Sahih and the Sunnah, indicating its methods, and the reason for what was exalted from it, and the reason for the inference of Al -Shafi'i if it was an inclination, and he responds to others such as Al -Tahwi from the Hanafi. Al -Bayhaqi also showed the doctrines of the followers and after them