This is a reference to the legal legacy of the Family of the Prophet being informed primarily by the teachings and practice of ʿAlī, his sons Ḥasan and Ḥusayn, ʿAlī Zayn al-ʿĀbidīn, Muḥammad al-Bāqir, and Jaʿfar al-Ṣādiq. Hossein Modarressi argues that it was with al-Bāqir that this legacy assumed formal shape as a systematic and well-organized tradition.
This source is part of the Online Companion to Hossein Modarressi, Text and Interpretation: Imam Jaʿfar al-Ṣādiq and His Legacy in Islamic Law (Harvard University Press, 2022).