(14) باب اسْتِحْبَابِ رَكْعَتَيْ سُنَّةِ الْفَجْرِ وَالْحَثِّ عَلَيْهِمَا وَتَخْفِيفِهِمَا وَالْمُحَافَظَةِ عَلَيْهِمَا وَبَيَانِ مَا يُسْتَحَبُّ أَنْ يُقْرَأَ فِيهِمَا
'A'isha reported that the Messenger of Allah (ﷺ) used to observe two (supererogatory) rak'ahs in between the call to prayer and the Iqama of the dawn prayer.
Reference: Sahih Muslim 724 c
In-book reference: Book 6, Hadith 113
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1568