In view of the then prevailing conducive political atmosphere, Imam Ja‘far as-Sadiq (‘a) pursued his father’s scientific movement and established a large university and center of learning whose horizon reached far and wide. Shaykh al-Mufid says: The knowledge of the Imam (‘a) has been so widely narrated that it became proverbial to various many and its fame spread to every nook and corner. None of the progeny of the Prophet (S) match him (in this regard) whose knowledge and learning have been so widely transmitted.
Amir ‘Ali thus writes about the Imam (‘a): Those philosophical discussions and debates in all the Islamic centers became widespread and the guidance and instructions given in this regard were made possible only by the university that has been established in Medina under the supervision of Hadrat Sadiq, a great grandchild of Hadrat ‘Ali. He has been one of the great ‘ulama’ with precise views, a deep understanding, and well-versed in all the branches of knowledge of the time. In reality, it is he who is the founder of the rational academy in Islam.
As such, those who were lovers of knowledge {‘ilm} and thirsty for the Muhammadan (S) gnosis {ma‘rifah} rushed from different parts of the then Muslim world to that heroic Imam (‘a) in multitude, and benefited from his abundant spring of knowledge and wisdom. Sayyid Ilahil says: “In Kufah, Basrah, Wasit, and Hijaz, people of every tribe sent their children to Ja‘far ibn Muhammad. Many of the Arabs and Persians, the people of Qum in particular, came to him.”
In his Al-Mu‘tabar, the late Muhaqqiq (al-Hilli) thus writes: During the period of Imam as-Sadiq (‘a) various branches of knowledge that were transmitted from him astonished the great thinkers. A group of about four thousand rijali scholars have narrated hadiths from him, and by his teachings a great number of people in the various sciences attained mastery to such an extent that his answers to their questions were compiled in four hundred books {musannafat}, which were called “Usul”.
In his book, Dhikra, Shahid al-Awwal also says: “Four thousand people from Iraq, Hijaz, Khurasan, and Sham put into writing the answers of Abu ‘Abd Allah Imam as-Sadiq (‘a) to the questions.”
In this manner, the seekers and lovers of knowledge and learning used to benefit from the Imam (‘a). Outstanding scholars in various branches of the revealed {naqli} and rational {‘aqli} sciences of the day such as Hisham ibn Hakam, Muhammad ibn Muslim, Aban ibn Taghlib, Hisham ibn Salim, Mu’min Taq, Mufadhdhal ibn ‘Umar, Jabir ibn Hayyan, etc. were trained under the blessing of his presence.
Their compilations which are known as the Usul Arba‘ami’ah, are the basis of the four Shi‘ah books on hadith, viz. Al-Kafi, Man La Yahdharah al-Faqih, At-Tahdhib, and Al-Istibsar.
The disciples of Imam as-Sadiq (‘a) were not all Shi‘ah as most of the Sunni scholars of the day have also studied under his guidance. Ibn Hajar al-Haythami, a Sunni author, thus writes in this regard: “The leading figures (in jurisprudence and hadith) such as Yahya ibn Sa‘d, Ibn Jarih, Malik, Sufyan ath-Thawri, Sufyan ibn ‘Uyaynah, Abu Hanifah, Sha‘bi, and Ayyub Sijistani have narrated hadiths on his authority.”
Abu Hanifah, the founder of the Hanafi school of thought, has said: I used to go to Ja‘far ibn Muhammad for sometime. I used to see him in one of the three conditions: either he was praying, in the state of fasting, or reading the Qur’an. I never saw him narrating the hadith without performing ablution. The one superior to Ja‘far ibn Muhammad in knowledge, devotion and piety has not been seen by any eye, heard by any ear, or perceived by any heart.
The Imam’s (‘a) teaching sessions were attended by those who later founded schools of jurisprudence attending as philosophers, as well as students of philosophy from far and wide. After learning the sciences from their Imam (‘a), they would return to their homelands and conduct teaching sessions of their own.
The Muslims used to gather around them and they in turn impart the teachings of the Ahl al-Bayt (‘a) propagating Shi‘ism. When Aban ibn Taghlib would come to Masjid an-Nabi, the people would reserve for him the pillar against which the Prophet (S) used to lean, and he would narrate hadiths to them. Imam as-Sadiq (‘a) used to say to him: “Sit in the mosque of Medina and issue religious edicts to the people as I like persons like you to be seen among my Shi‘ah.”
Aban was the first person to have written something on the sciences of the Qur’an {‘ulum al-Qur’an} and he was also so well-versed in hadith that he used to sit in Masjid an-Nabi and the people would come and ask him. Through his various styles of speaking, he would answer them and impart the hadiths of the Ahl al-Bayt (‘a) to them.
In Mizan al-I‘tidal, adh-Dhahabi thus says regarding him: “If the hadith of individuals such as Aban who are accused of being Shi‘ah is rejected, a great part of the Prophetic works would have perished.”
Abu Khalid al-Kabuli says: “I saw Abu Ja‘far Mu’min Taq sitting in Masjid an-Nabi while the people of Medina gathered around him and posed their questions on jurisprudence {masa’il} to him and he would answer them.”
Shi‘ism during that period was so spread that some people, in a bid to acquire social standing among the people, resorted to fabricating hadiths from the Imams (‘a) to draw people’s attention by interpreting the traditions in their own favor.
For example, Imam as-Sadiq (‘a) - in reply to one of his companions named Faydh ibn Mukhtar who asked about the reason behind the contradiction in hadiths—thus says: “These people are not seeking the pleasure of Allah in narrating the hadiths and expressing our views. They are rather seeking the world and each of them is aspiring to be leader.”