It was narrated that Abdullah said:"My sister Hafsah told me that he used to pray two brief rak'ahs before Fajr."
أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا خَالِدُ بْنُ الْحَارِثِ، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ، قَالَ حَدَّثَتْنِي أُخْتِي، حَفْصَةُ أَنَّهُ كَانَ يُصَلِّي قَبْلَ الْفَجْرِ رَكْعَتَيْنِ خَفِيفَتَيْنِ .
Nesai
The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day • Hadith 1774