Therefore...

Therefore, he was able to pass down the authentic teachings of the Noble Qur’an and the and crystallize them in what came to be known as al-Fiqh al-Ja‘fari , the Ja‘fari Jurisprudence. His teachings were collected in 400 usul (foundations) which were written by his students and encompass hadith, Islamic philosophy, theology, commentary of the Qur’an, literature, and ethics.

After a period of time, three distinguished scholars categorized these 400 usul in four books which are the main sources of hadith for the Shi‘a school of thought. They are: Usul al-Kafi by al-Kulayni (d.329H), Man La Yahduruh al-Faqih by al-Saduq (d.381H), and al-Tahdib and al-Istibsar by al-Tusi (d.460H). These three scholars were known as the “three Muhammads” since their first names were all Muhammad.

While these four books are the main sources of hadith for the Shi‘a, their authors still did not label their books as “ sahih ” (authentic). Although they did their best to gather only authentic traditions, but if a particular tradition contradicted the Noble Qur’an then it was not accepted as legal and valid. Hadith, according to the Ja‘fari school of thought, are accepted only if the Noble Qur’an verifies them, since the Noble Qur’an is the only undoubtable source of guidance.

Hanafi The Hanafi school of thought was headed by Imam al-Nu΄man ibn Thabit (Abu Hanifa) who lived from 80H to 150H. Imam Abu Hanifa was born to a non-Arab father, was raised in Kufa, and died in Baghdad.

This school of thought prevailed during the time of the Abbasid Empire when a student of Imam Abu Hanifa, Abu Yusuf al-Qadi became the head of the judiciary department and the highest judge, and thus he spread this madhhab (school of thought), in particular, during the caliphates of al-Mahdi, al-Hadi, and al-Rashid.

No other man was as close to the Abbasid caliph, Harun al-Rashid as was Abu Yusuf al-Qadi, but the Abbasid caliph, al-Mansur also worked hard to support and consolidate Imam Abu Hanifa’s school of thought and to spread his madhhab in the face of the growing popularity of Imam Ja‘far al-Sadiq.

Imam Abu Hanifa studied under the instruction of Imam Ja‘far al-Sadiq for two years,[^2] and said in regards to him, “I have not seen anyone more knowledgeable than Ja‘far ibn Muhammad, and indeed, he is the most knowledgeable one in the nation.”[^3] Maliki The Maliki school of thought was headed by Imam Malik ibn Anas al-Asbahi who lived from 93H to 179H.