Sahih Muslim
Sahih Muslim 723 e
It is recommended to pray two rak`ah for the sunnah of Fajr. And encouragement to pray them regularly, and to make them brief, and to persist in offering them, and clarifying what is recommended to recite therein
Arabic hadith text
حَدَّثَنَا مُحَمَّدُ بْنُ عَبَّادٍ، حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرٍو، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، أَخْبَرَتْنِي حَفْصَةُ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَإِذَا أَضَاءَ لَهُ الْفَجْرُ صَلَّى رَكْعَتَيْنِ .
Translation
Hafsa reported
When the dawn appeared, the Messenger of Allah (ﷺ) observed two rak'ahs (of Sunnah prayers).