It is narrated from Sayyiduna Abu Maryam (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) slept at the start of the morning and did not wake up until the sun had risen. When he woke, the Messenger of Allah (peace and blessings be upon him) instructed Sayyiduna Bilal (may Allah be pleased with him), who gave the call to prayer. Then he (peace and blessings be upon him) prayed two rak'ahs, then gave the instruction and led the Fajr prayer.
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16651