This is a reference to the tradition of the House of the Prophet that held the call to prayer (adhān) to be taught to the Prophet by the angel Gabriel. Hossein Modarressi cites this reference as an example of how the tradition of the House of the Prophet compared to the Sunnī belief that the call to prayer originated in a Companion's dream.
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).