The versatile genius of Imam Ja'far As-Sadiq in all branches of knowledge was acclaimed throughout the Islamic world, which attracted students from far-off places towards him till the strength of his disciples had reached four thousand. The scholars and experts in Divine Law have quoted many traditions from Imam Ja'far As-Sadiq. His disciples compiled hundreds of books on various branches of science and arts. Other than Fiqh (Islamic jurisprudence), Hadith (tradition), Tafsir (exegesis of the Holy Qur'an), etc., the Holy Imam also imparted mathematics and chemistry to some of his disciples. Jabir ibn Hayyan, a famous scholar of Chemistry and Mathematics, was one of the Imam's disciples who benefited from the Imam's knowledge and guidance and was able to write four hundred books on different subjects.
It is an undeniable historical truth that all the great scholars of Islam were indebted for their learning to the very presence of the AhluI-Bayt who were the fountain of knowledge and learning for all. Ash-Shibli one of Sunni outstanding scholars writes in his book Siratu'n- Nu'man: "Abu Hanifah remained for a considerable period in the attendance of Imam Ja'far As-Sadiq, acquiring from him a great deal of precious research on Fiqh and Hadith. Both the sects -Shi'a and Sunni- believe that the source of Abu Hanifah's knowledge was mostly derived from his association with Imam Ja'far As-Sadiq." The Imam devoted his whole life to the cause of religious preaching and propagation of the teachings of the Holy Prophet and never strove for power. Because of his great knowledge and fine teaching, the people gathered around him, giving devotion and respect that was his due. This excited the envy of the 'Abbasid ruler al-Mansur Ad-Dawaniqi who fearing the popularity of the Imam, decided to do away with him.
The number of traditions preserved from the Fifth and Sixth Imams is more than all the hadith that have been recorded from the Prophet and the other ten Imams combined.
But toward the end of his life the Imam As-Sadiq was subjected to severe restrictions placed upon him by the Abbasid caliph Al-Mansur, who ordered such torture and merciless killing of many of the descendants of the Prophet who were Shia that his actions even surpassed the cruelty and heedlessness of the Umayyad. At his order they were arrested in groups, some thrown into deep and dark prisons and tortured until they died, while others were beheaded or buried alive or placed at the base of or between walls of buildings, and walls were constructed over them. Hisham, the Umayyad caliph, had ordered the Sixth Imam to be arrested and brought to Damascus.
Later, the Imam was arrested by As-Saffah, the Abbasid caliph, and brought to Iraq. Finally, Al-Mansur had him arrested again and brought to Samarrah where he had the Imam kept under supervision, was in every way harsh and discourteous to him, and several times thought of killing him. Eventually the Imam was allowed to return to Medina where he spent the rest of his life in hiding, until he was poisoned and martyred through the intrigue of Al-Mansur. Upon hearing the news of the Imam's martyrdom, Al-Mansur wrote to the governor of Medina instructing him to go to the house of the Imam on the pretext of expressing his condolences to the family, to ask for the Imam's will and testament and read it. Whoever was chosen by the Imam as his inheritor and successor should be beheaded on the spot. Of course, the aim of Al-Mansur was to put an end to the whole question of the Imamate and to Shia aspirations. When the governor of Medina, following orders, read the last will and testament, he saw that the Imam had chosen five people rather than one to administer his last will and testament: the caliph him- self, the governor of Medina, 'Abdullah Aftah, Abdullah the Imam's older son, and Musa Al-Kadhim, his younger son and Hamidah Musa Al-Kadhims Mother. In this way the plot of al-Mansur failed.
