Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that Hafsah (may Allah be pleased with her), the wife of the Prophet (peace and blessings be upon him), told me that he (peace and blessings be upon him) used to pray two rak'ahs before Fajr and keep them light.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19627