Jaʿfar b. Muḥammad b. ʿAlī b. al-Ḥusayn (a) (Arabic: جعفر بن محمد بن علي بن الحسین), (b. 83/702 – d. 148/765) known as Imām al-Ṣādiq (a) (الإمام الصادق), is the sixth Imam of Imamiyya and the fifth Imam of Isam'ilis. His Imamate lasted 34 (lunar) years (114/733 - 148/765) and was concurrent with the reign of the last five Umayyad caliphs (that is, from Hisham b. 'Abd al-Malik onwards) and with that of the first two Abbasid caliphs, al-Saffah and al-Mansur al-Dawaniqi. Because of the weakness of the Umayyad rule at his time, Imam al-Sadiq (a) 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 al-Bayt (a) recorded in Twelver Shiite hadith collections are from Imam al-Sadiq (a). This is why Imamiyya is called Ja'fari School. Imam al-Sadiq (a) has had a high status in the eyes of prominent Sunni scholars. Abu Hanifa and Malik b. Anas were among the people who quoted hadiths from him.