(14) باب اسْتِحْبَابِ رَكْعَتَيْ سُنَّةِ الْفَجْرِ وَالْحَثِّ عَلَيْهِمَا وَتَخْفِيفِهِمَا وَالْمُحَافَظَةِ عَلَيْهِمَا وَبَيَانِ مَا يُسْتَحَبُّ أَنْ يُقْرَأَ فِيهِمَا
Hafsa reported:
When the dawn appeared, the Messenger of Allah (ﷺ) observed two rak'ahs (of Sunnah prayers).
Reference: Sahih Muslim 723 e
In-book reference: Book 6, Hadith 110
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1566