The science of "Usul al-Fiqh" is considered one of the most important legal sciences created by the mentality to serve Islamic law: it is the science that gives its learner and the adoption of the methods that the diligent imams followed in deriving their jurisprudence inherited through generations. He is also the most knowledgeable one who explains the features of the Sharia for those who want to derive the rulings of the Sharia in terms of events and developments that occur to people: so this announcement was necessary for those who wanted to know the jurisprudence of the predecessors and the rulings of the Sharia in various events. Imam al-Shafi’i (150-204 AH) was the first to write a future book on the science of “Usul al-Fiqh” and named his book as “The Message”. The scholars after al-Shafi’i continued to write books, small and large, on the science of fundamentals.