Shah Wali Allah belonged to the Hanafi school of fiqh, as did his forefathers. Shaykh Abu Tahir al-Kurdi, however, was a Shafi’i. This led Shah Wali Allah to treat the Hanafi and Shafi’i’ schools of fiqh with the same deference. Although in his home country he chose to follow the Hanafi school as far as practicable, he did not altogether dismiss the Shafi’i school. He based his study of Hanafi Fiqh on the works of al-Shaybani, and that of Shafi’i Fiqh directly on the works of al-Shafi’i. Noting that both al-Shaybani and al-Shafi’i had derived their Fiqh from Malik ibn Anas, Shah Wali Allah concluded that Malik’s Muwatta was the basis of all Fiqh, and that all the Fiqhi doctrines of the four Sunni schools had developped from the same roots. Since al-Muwatta had been compiled in Madinah, it represented the epitome of the juristic tradition of Madinah. This juristic tradition could be traced back to Umar ibn al-Khattab. As such, Shah Wali Allah considered these four schools to be a commentary on the juristic approach of Umar. Hence his assertion in his “Izalat al-Khafa’ ” that Umar was the absolute Mujtahid (al-Mujtahid al Mutlaq), while the three imams, in their relationship to Umar, were no more than Mujtahid Muntasib.
Shah Wali Allah felt that the Muwatta combined the method of the Fuqaha and that of the Muhaddithin, giving his students the advantages of both the Faqih and the Muhaddith. Moreover, it is considered to be the source of at least three schools of Sunni jurisprudence by most scholars; Wali Allah coniders it to be the basis of all four schools and says that these schools may be considered commentaries on the text of Muwatta.
[Islamic Renaissance in South Asia 1707-1867: The Role of Shah Wali Allah and His Successors, Mahmood Ahmad Ghazi, Adam Publishers, p157-158 & p161]