Jabir ibn Samurah relates that after Allahs Messeger Saws would perform Fajr, the used to remain seated in the place of prayer until the Sun had fully risen (Muslim)

The Messenger of Allah Saws said :

“Whoever offers Fajr in congregation & remains seated, engaging in the remembrance of Allah until the Sun has risen, & then offers 2 units of prayer, he will have a reward equal to that of performing HAJJ and Umrah.”

The Messenger of Allah swt said, “Complete, complete, complete. (ie complete reward).

Tirmidhi.