Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that Hafsah (may Allah be pleased with her) told me that he, meaning the Prophet (peace and blessings be upon him), used to pray two rak'ahs before Fajr.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19621