This is a reference to notable Sunnī jurists who attended Jaʿfar al-Ṣādiq's audience, including, for example, Rabīʿat al-Raʾy (d. 136 AH). Hossein Modarressi cites this reference in his discussion of some of the features of al-Ṣādiq's jurisprudence.
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).