Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that Hafsah (may Allah be pleased with her) told that when the dawn grew bright, the Prophet (peace and blessings be upon him) would pray the two rak'ahs of Fajr.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19679