Sayyiduna Abu Hurayrah (may Allah be pleased with him) states: Sayyiduna Bilal (may Allah be pleased with him) came to the Prophet (peace and blessings be upon him) at the time of the morning adhan and found him asleep. He called out aloud, addressing the Prophet (peace and blessings be upon him): "Prayer is better than sleep." The Prophet (peace and blessings be upon him) did not object to it, and he included these words in the adhan. They did not give the adhan for any prayer before its appointed time except the Fajr prayer.
Imam al-Tabarani recorded this narration in al-Mu'jam al-Awsat, and he says: Marwan bin Thawban is alone in narrating it. (Allamah al-Haythami says:) I say: I have not found anyone who mentions him.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1859