Musnad Ahmad Hadith 5490

Anas bin Sirin, may Allah have mercy on him, says that I once asked Ibn Umar, may Allah be pleased with them both, which surahs should I recite in the Sunnah of Fajr? He replied that the Prophet, peace and blessings be upon him, used to pray the night prayer in sets of two rak'ahs. I said, I am asking you about the Sunnah of Fajr. He said: You are a man of thick intellect, do you not see that I am just beginning to speak? The Prophet, peace and blessings be upon him, used to pray the night prayer in sets of two rak'ahs, and when he feared the approach of true dawn, he would add one rak'ah and perform Witr, then he would lay his head down and rest, then get up and pray the Sunnah of Fajr at the time when the sound of the adhan was reaching his ears.