Rasool Allah sallallahu alayhi wasallam said:
مَنْ صَلَّى الْفَجْرَ في جَمَاعَةٍ ثُمَّ قَعَدَ يَذْكُرُ الله حَتَّى تَطْلُعَ الشَّمْسُ ثُمَّ صَلَّى رَكْعَتَيْنِ كانَتْ لَهُ كَأَجْرِ حَجَّةٍ وَعُمْرَةٍ تَامَّةٍ تَامَّةٍ تَامَّةٍ
Whoever prays fajr in congregation then sits remembering Allah until the sun rises, then prays two rak’ahs will have a reward like that of hajj and umrah … complete,complete,complete.
[Saheeh Al Jaami # 6346]
مَنْ صَلَّى الْفَجْرَ في جَمَاعَةٍ ثُمَّ قَعَدَ يَذْكُرُ الله حَتَّى تَطْلُعَ الشَّمْسُ ثُمَّ صَلَّى رَكْعَتَيْنِ كانَتْ لَهُ كَأَجْرِ حَجَّةٍ وَعُمْرَةٍ تَامَّةٍ تَامَّةٍ تَامَّةٍ
Whoever prays fajr in congregation then sits remembering Allah until the sun rises, then prays two rak’ahs will have a reward like that of hajj and umrah … complete,complete,complete.
[Saheeh Al Jaami # 6346]