Imam Sadiq (pbuh) lived at a time when there was a deep and active interaction between Islamic thought and knowledge and the peoples of other nations. During that era, numerous works from different scholars and thinkers were widely translated into various languages. Sciences, philosophies and thought from other nations, too, were translated from their native languages into Arabic. Muslims studied these sciences, added to them, enriched them, and broadened their scopes. As a result, an active, ideological and scientific movement emerged. Muslims indulged in the sciences of medicine, astronomy, chemistry, physics, and mathematics, among other ones. Philosophy, logic, the fundamentals of reasoning and other sciences were translated especially from Greek and the Persian languages.
It was during these times that the Muslims were also introduced to a new line of philosophical thought. This cultural interaction and intrusion that had both its pros and cons did not pass without drawing reactions from the Muslims. Consequently, a current of suspicion, complication, and unbelief rose in the Muslim community. Groups of people started adopting dialectics and embracing deviant views. But after a long and bitter struggle as well as long drawn out ideological fighting, the solid Muslim domestic front succeeded in stopping the cultural invasion, and exposing its flaws and weaknesses.
In addition to these scientific and cultural developments, during Imam Sadiq's (pbuh) times, there wasa remarkably great movement in many fields. New political, economic, and social events and problems surfaced which needed to be settled according to Islamic laws. The consequent result was the emergence of new, unheard-of views and schools of thought. Scholars (ulama) became actively involved in trying to deduce the right answers for the new problems.
Amid these hard conditions and the scientific and cultural activities, after the emergence of alien schools of thought, Imam Sadiq (pbuh) lived and carried out his responsibilities, as a scholar and an unmatched teacher in the cultural and religious domains. Hard, though the rulers and their hired writers tried to obliterate the image of this great man, he remained a shining star in the sky of Islam, and a rich spring of Islamic knowledge.
During his father Imam Baqir's lifetime, Imam Sadiq (pbuh) helped in the establishment of the Ahl ul-Bait University in the Mosque of the Prophet (pbuh). Both these Imams spread pure knowledge throughout the Islamic homeland - among the circles of jurisprudents (fuqaha), preachers, philosophers - and other scholars highly praised Imam Sadiq (pbuh) and his firm scientific background.
In the words of Sheikh Mufid: "From among all his brothers, (Imam) Sadiq, Jafar bin Muhammad bin Ali bin Hosein (pbuh) emerged as the successor to his father Baqir, Muhammad bin Ali (pbuh), and as his trustee and the next Imam after him. He was distinguished among his people by his virtues. He was the cleverest, the greatest in stature, and the most venerated among the scholars and the common people. People took from him so much knowledge that men conveyed it to the remotest areas. He was well known in all parts of the Islamic lands. No other member of the Ahl ul-Bait matched him in being the conveyor of so much scientific knowledge. No other member of the Ahl ul-Bait was also remembered and praised by the historians and biographers as he was. Nor had the historians ever quantitatively reported from anyone as they had done from Abu Abdillah (Imam Sadiq) (pbuh). Scholars concerned with the Prophetic Traditions (Ahadith) made a list of the authoritative narrators from different schools of thought who reported from Imam Sadiq (pbuh)- they amounted to 4,000 men.
The great scholar, Allamah Sayyid Muhsin Amin in his book, Manaqib Aal Abi Talib (Virtues of the Family of Abi Talib) says that Bin Shahrashub quotes Abu Naim as writing in his book Al-Hilyah, "The Ornament", as follows:
"Umar bin Muqdam said: Whenever I looked at Jafar bin Muhammad (pbuh), I would know that he was a descendant of the line of the Prophets (PBUT). Never did a book on Prophetic Traditions, wisdom, asceticism, or morals, contradict his words. They said: Jafar bin Muhammad Sadiq (pbuh) said an-Naqqash, al-Thalabi, al-Qishri and al-Qizwini mentioned him in their Qur'anic exegeses."
The famous historian, Al-Yaqubi described him in these words:
"He was the best of men, and the most knowledgeable about the faith. The famous intellectuals who learned from him would refer to him, when quoting him as, `The Scholar told us....'."
Muhammad Farid Wajdi, the compiler of Dairat Ma'arif al-Qarn al-Ishrin (the 20th Century Encyclopedia) writes thus about Jafar bin Muhammad Sadiq (pbuh), the sixth Imam of the Shi'as:
"Abu Abdillah Jafar bin Muhammad Sadiq bin Muhammad Baqir bin Zain al-Abidin bin Hosein bin Ali bin Abi Talib (pbuh) was one of the leading men of the Household of the Prophet (pbuh). His words were always true hence the title "Sadiq". He was one of the most virtuous among people. In the field of chemistry, he wrote and expressed views."
In his book Al-Milal wa al-Nihal (Religions and Creeds) Abul Fath Shahristani writes:
"Imam Jafar Sadiq (pbuh) was a man of immense knowledge in religion; complete competence in wisdom; extreme asceticism in life; and thorough piety; thus, protecting him against committing sins. He settled in Medina, benefiting the Muslims who followed him; and conferring on the trustworthy ones, the secrets of sciences. He then went on to Iraq and stayed there for sometime, during which he never got involved in fighting over the right to caliphate. He who is drowned in the Sea of Knowledge, never covets a seashore, nor does the one who attains the pinnacle of truth fear falling."
The founder of the Malikis (an Islamic School of Thought), Sheikh Malik bin Anas describes Imam Jafar Sadiq (pbuh) as follows:
"Occasionally, I met Jafar bin Muhammad (pbuh). He had a smiling disposition and a sense of humor. When the Prophet (pbuh) was mentioned, his face would turn pale. For some time that I visited him regularly, I would see him doing one of these three things: Praying, fasting or reciting the Qur'an; He would first make ablution before citing Prophetic Traditions. He never talked about anything that did not concern him."
In his introduction to the book, Imam Sadiq (pbuh), Sheikh Muhammad Abu Zahrah, writes:
"With the help and blessings of Allah, we had decided to write about Imam Jafar Sadiq (pbuh). We had already earlier written about seven of the honorable Imams (pbuh). We have not delayed writing about Imam as-Sadiq because he is less meritorious than them. On the contrary, he matched the seven Imams in his virtues. He is distinguished from the great men by his outstanding merits."
Abu Hanifah has been quoted saying: "He (Imam Sadiq) believed he was the most knowledgeable man among people, though diverse their opinions were. He was the most well versedfaqih. Malik used to call on him as a scholar and a narrator of Traditions. He was the teacher of Malik and Abi Hanifa, and even if that were his only credit it would be enough for him. Nor would there be a man who could exceed him in his virtues. And above all that, he was the grandson of Zain Abidin (pbuh), who was the master of the city of Medina in his time; due to his virtues, honor, faith, and knowledge. Among his students was Ibn Shihab Zuhri and others from the later generations of Muslims. He is the son of Muhammad Baqir (pbuh) who slashed the `knowledge' open and got its kernel. He was the one on whom Allah, the Exalted, bestowed great personal honor and the additional honor of being from a noble lineage of the Household of Muhammad (pbuh).
Thus was the great Imam of the Muslims, the Master of the Fuqaha and the Eloquent, and the worthy Scion of Prophethood - Imam Jafar Sadiq (pbuh) - May Allah bless him.
source : tebyan