Ash-Shaafi’iy founded the ‘Ilm of Usool ul-Fiqh and this was received (well) by the ‘Ulamaa and Fuqahaa, who followed him, through examination and study. So they added to it and revised a number of issues within it until it became an ‘Ilm that was coherent, clear and distinguished in its features, due to the firm foundation that Al-Imaam Ash-Shaafi’iy laid down solidly for this noble knowledge.

Ash-Shaafi’iy did not reach the point of completion in respect to Usool ul-Fiqh and so others came to complete the building that he had begun. There were from amongst them those who followed him providing explanation and elaboration, there were also those who came adding new principles whilst others came critiquing and disagreeing with him in respect to some of the Qawaa’id (principles).

These areas of study after Ash-Shafi’iy were restricted to specific subjects in Usool ul-Fiqh and they did not deal with Usool ul-Fiqh as a whole. They were restricted to subjects in respect to explanation, addition and disagreement.

The most prominent explanations (Shurooh) of Ash-Shaafi’iy’s Risaalah in Usool ul-Fiqh were:

1) The Sharh (explanation) of Abu Bakr Muhammad As-Seerfiy who passed away in the year 330 AH and it was called: ‘Dalaa’il Al-I’laam’.

2) The Sharh of Muhammad Al-Qaffaal Ash-Shaashii who passed away in the year 365 AH.

3) The Sharh of Abu Muhammad Abdullah ibn Yousuf Al-Juwainiy who passed away in the year 438 AH.

From the earliest of those who wrote in Masaa’il (issues) of Usool ul-Fiqh after Ash-Shaafi’iy were:

1) Al-Imaam Ahmad Bin Hanbal in his book: ‘Taa’at Ar-Rasool’, the book: ‘An-Naasikh Wa-l-Mansookh’ and the book: ‘Al-‘Ilal’.

2) Daawud Azh-Zhaahiriy in the book: ‘Ibtaal Al-Qiyaas’ and the book: ‘Al-Khusoos Wa-l-‘Umoom’ amongst others. Most of what he wrote was a critique of the Usool of Ash-Shaafi’iy.

3) Muhammad At-Tirmidhi who passed away in the year 255 in the book: ‘Ithbaat Al-‘Ilal Ash-Shar’iyah’.

Most of these books were lost and it is clear to us from their headings and titles that they were restricted to dealing with issues of disagreement or difference; either in support of Ash-Shaafi’iy and as a rebuttal to those who disagreed with him, or they were to establish the Madh’hab of the writer and as a rebuttal in opposition to the Madh’hab of Ash-Shaafi’iy.