I asked Jabir bin Samura, "Did you used to sit with the Messenger of Allah ﷺ?"He replied, "Yes, often. He would not get up from the spot where he prayed the dawn prayer until the sun had risen, and once it rose, he would stand up. The companions would talk among themselves, recounting matters from the days of ignorance, and they would laugh while he would smile."
قلت لجابر بن سمرة: أكنت تجالس رسول الله ﷺ؟ قال: نعم كثيرا، كان لا يقوم من مصلاه الذي يصلي فيه الصبح أو الغداة حتى تطلع الشمس، فإذا طلعت الشمس قام. وكانوا يتحدثون، فيأخذون في أمر الجاهلية، فيضحكون ويتبسم.
Muslim narrated it in "Mosques" (670) through Abu Khaythama, from Simak bin Harb, who mentioned something similar. Sufyan and Zakariya both narrated it from Simak with this wording, that the Prophet ﷺ, when he prayed Fajr, would sit in his place of prayer until the sun rose fully. His saying "fully" means high up.