The sixth Shia Imam’s Imamate lasted 34 (lunar) years (114/733 - 148/765) and was concurrent with the reign of the last five Umayyad caliphs and with that of the first two Abbasid caliphs.
Because of the weakness of the Umayyad rule at his time, Imam Sadeq (AS) was able to have relatively wider scholarly activities.
His companions, students, and those who quoted hadiths from him is said to have amounted to four-thousand people. Most of the hadiths of Ahl-ul-Bayt (AS) recorded in Twelver Shia hadith collections are from Imam Sadeq (AS). This is why Imamiyya is called Jafari School.
Imam Sadeq (AS) was martyred in 765 AD in Medina. He was buried in the Baqi Cemetery in Medina beside his father Imam Baqir (AS), his grandfather Imam Sajjad (AS) and his uncle Imam Hasan (AS).