Aishah (may Allah be pleased with her) said that the Messenger of Allah (peace and blessings be upon him) would pray the two rak'ahs of Fajr; if I was awake he would talk with me, otherwise he would lie down, then he would go to the prayer.
(b) Malik bin Anas (may Allah have mercy on him) narrated it, outside the Muwatta, from Salim Abu al-Nadr; he placed the hadith right after the night prayer, and mentioned that he (peace and blessings be upon him) would lie down after two rak'ahs that came before the two rak'ahs of Fajr.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4889