Al-Uṣūl al-arbaʿamiʾa (Arabic: الاصول الاربعمائة, the four hundred principles) are four hundred hadith collections which were collected by the transmitters of hadith directly from the Prophet (s) and Imams (a) in the early centuries of Islam.
They were sources for later hadith references, and one criterion of authenticity for next generation of hadith scholars was the existence of at least one of these "usul" in the reference of a hadith.
The content of these collections was hadiths from the Infallible Imams (a) in different fields of rulings, traditions, sermons, supplications, and commentaries of the Qur'an. Collecting them was being carried out by the companions of Imams from the time of Imam 'Ali (a) until Imam Hasan al-Askari (a) and the number of those companions has sometimes been reported to have been exactly four hundred, most of whom were companions of Imam Ja'far al-Sadiq (a).
Difference between Asl and Kitab
"Usul" is the plural form of "Asl" and in the Twelvers' works, there is a difference between asl (literally, "primary") and kitab (literally, "book") or musannaf ("written work"). For example, sometimes in the books of rijal, a transmitter is introduced as "he has authored a kitab and also an asl." About the difference between a kitab and an asl, it has been said that, "In case of a kitab or a musannaf, the author is engaged in writing and any modification to the work, while in writing an asl, the author would only record and compile anything he has heard."
Some others have distinguished the two types of works as follows: "Asl is a reliable collection, the hadiths in which are not adopted from another book." "Asl is a collection, the hadiths in which are reported directly from an Infallible Imam (a), but a kitab is a collection of hadiths which are adopted from an asl."
Aqa Buzurg Tihrani wrote, "In hadith studies, asl is a certain part of hadith books, but a kitab might include any writing about hadiths. Asl is used as in its literal sense, because if the book of hadiths is comprised of the sayings of the Infallible (a), such hadiths are primary and original proofs for those who want to write anything about hadiths and thus such collections are called asl", but a kitab can include hadiths and the author's own understandings as well.
Apparently, the trustworthiness of such usul is that the companions of Imams (a) would instantly write down hadiths from them upon hearing them which lowered the possibility of forgetting them or modification of their wording. This claim is approved by al-Sayyid b. Tawus's report in Muhaj al-da'awat saying that, "a group of the companions of Imam al-Kazim (a) would attend his presence having pen and paper and recorded anything he said or any ruling he gave."
There were more than four hundred usul available at the time of Imams (a), however those which were verified and approved by Twelver Shi'as have been four hundred ones.
The authors of those four hundred usul have been all reliable and trustworthy, however, they were not all Twelver Shi'a. In al-Fihrist, al-Shaykh al-Tusi says, "Although some of the Shi'a authors of the usul have been following corrupted schools, their works (in trustworthiness and authenticity) are reliable."
In Mashriq al-shamsayn, Baha' al-Din al-'Amili, said that an evidence of authenticity of a hadith for Shi'a scholars was its appearance in some usul or its repetition in one asl or existence of a hadith in an asl, the author of which has been among definitely reliable people (People of Consensus) to Shi'a and that also has been early Shi'a scholars' proof for validity of the content of the mentioned usul.
Before writing the Four Books (al-Kafi, Man la yahduruh al-faqih, al-Tahdhib, and al-Istibsar) usul have been carefully preserved and kept safe. However, after the Four Books, there was less care about guarding the usul; mostly due to lack of order in their topics which made the reader's access to them difficult. On the other hand, the Four Books had included and arranged all the content of those usul.
Most usul have been available in their original form until the time of Ibn Idris al-Hilli (d. About 598/1201-2). At the end of al-Sara'ir, he quoted some hadiths from them in a section called Mustatrafat al-sara'ir.
Name of Some of the Authors
These are some of the authors of usul:
- Zayd al-Zarrad
- 'Asim b. Hamid al-Hannat al-Kufi
- Ja'far b. Muhammad al-Hadrami
- Musa b. Bakr al-Wasiti
- Mu'awiya b. 'Ammar
- Ahmad b. Abi Nasr al-Bazanti
- Aban b. Taghlib
- Zurara b. A'yan
- Abu Basir
- Muhammad b. Muslim
- 'Abd Allah b. Bukayr
- Yunis b. 'Abd al-Rahman
- Safwan b. Yahya
- Ibn Abi 'Umayr
- Ahmad b. Muhammad al-Bazanti
- 'Abd al-Malik b. Hakim al-Khath'ami
- Muthanna b. al-Walid al-Hannat
- Khallad al-Sindi
- Al-Husayn b. 'Uthman al-'Amiri
- 'Abd َAllah b. Yahya al-Kahili
- Mamqani. Talkhis miqbas al-hidaya. vol. 3. p. 26.
- Mamaqani. Talkhis miqbas al-hidaya. vol. 3. p. 26.
- Agha Buzurg. al-Dhari'a. vol. 2. p.126.
- Agha Buzurg. al-Dhari'a, vol. 2. p. 127.
- Bahrani. al-Hada'iq al-nadira, vol. 1. pp. 17 - 21.
- al-Shikh al-Tusi. al-Fihrist. p. 2.
- al-Baha'i. Mashriq al-shamsayn. pp. 26-27.
- Agha Buzurg. al-Dhari'a. vol. 2. p. 134.
- Aqa Buzurg, Tihrani. al-Dhari'a ila tasanif al-Shi'a. Beirut: Dar al-Adwa'. 1403 AH.
- Al-Bahrani, Yusuf, al-Hada'iq al-nadira, Mu'assisat al-Nashr al-Islami.
- Al-Shaykh al-Baha'i. Mashriq al-shamsayn wa iksir al-sa'adatayn ma' ta'liqat al-Khawaju'i. ed. Mahdi Raja'i. Mashhad: Astan al-Razawi al-Muqaddasa.
- Al-Shaykh al-Tusi, Muhammad b. al-Hasan. al-Fihrist. revised by Jawad Qayyumi. Qom: Nashr al-Fiqaha. 1417 AH.
- Mamaqani, Abd Allah. Talkhis miqbas al-hidaya. summarized by 'Ali Akbar Ghaffari. Tehran: Saduq Publication. 1991.