- witnesses: This was the generation of the Companions of the Prophet (ﷺ) who saw, heard and lived with him. They witnessed the revelation and application of the Qur’an and Sunnah. They observed how he handled cases that were not responded to directly by revelation. They had the entire Qur’an transcribed. Many of the Companions spread out into the rest of the Ummah after the death of the Prophet (ﷺ) to teach and guide people. This period lasted till approximately the end of the first Hijrah century.
- The Generation of Jam’i – of gatherers, collectors: This was the generation of the students of the companions of the Prophet. They were taught by the Companions who learned directly from the Prophet (ﷺ). They gathered what they learnt from the companions in book form. They were the Tabi’in (the Followers of the Companions of the Prophet (ﷺ).
- The Generation of Fiqh and Usul al-Fiqh – of analysts and jurists: This is the time of the Successors (or Followers) of the Followers of the Companions of the Prophet (ﷺ), the Tabi’u al-Tabi’in. It was during this period that a more structured and systematised approach (tadween) of analysing Islamic law was developed, based on what the Tabi’u al-Tabi’in heard from their teachers who were taught by the companions of Prophet (ﷺ). Fiqh by definition has to be based on principles (usul) and grounded in evidence (adillah) and therefore on an Usul al-Fiqh. So, while earlier jurists employed well-developed principles and methodologies that guided their juristic reasoning (ijtihad), the first writing and articulation of Usul al-Fiqh as an independent science was done by Imam Shafi’i. 
Fiqh is an Arabic term which literally means “deep understanding” but has come to denote the broad field of Islamic Jurisprudence. The great jurists, Imam Nu’man bin Thabit Abu Hanifa (d. 150 AH), Imam Malik bin Anas (d. 179 AH), Imam Muhammad bin Idris Shafi’i (d. 204 AH) and Imam Ahmad bin Hanbal (d. 241 AH) were scholars of Fiqh. The chart below shows their line of teachers.
The chart below shows the lapse of time between the Prophet Muhammad (ﷺ)’s life and period of the development of Fiqh, derived using Usul al-Fiqh. Imam al-Bukhari and Imam Muslim were not well known as fuqahabut as later compilers and authenticators of oral and written traditions (Hadith).
Source: Tariq Ramadan, To Be a European Muslim, The Islamic Foundation, Leicester, 1999
 The words “successors” and “followers” as in “Followers of the Successors” are used interchangeably.
 Shaykh Abdallah Bin Bayyah, The Legal Philosophy of Islam (Qawa’id al-Fiqhhiyyah), trnsl., Hamza Yusuf, CD lecture series in Zaytuna Institute, Al-Hambra Productions, California, USA., 2000; Musa bin Muhammad bin Yahya al-Qarni, Murtaqa al-UsulIlaTarikhIlm al-Usul, Medina, 1414 AH, p.5; Mohammad Akram Laldin, Introduction to Shari’ah and Islamic Jurisprudence, 2nd ed. CERT, Kuala Lumpur, 2008, p.155-221; Jasser Auda, Maqasid al-Shariah as Philosophy of Islamic Law, IIIT, Herndon, 2008, p.60-75.
 Plural of faqih – a specialist in Islamic Jurisprudence. Though some scholars regard Imam Bukhari as also being a Mujtahid in addition to being a scholar of hadith (Muhaddith). See Gibril Fouad Haddad, The Four Imams and their Schools, Muslim Academic Trust, London, UK., nd., p.iix