It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that 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 (peace and blessings be upon him) asleep, so he called out: "Al-salatu khayrun min al-nawm" (Prayer is better than sleep). The Messenger of Allah (peace and blessings be upon him) did not object to it and included it in the adhan; and the adhan is not given for any prayer before its time except the Fajr prayer.
Imam al-Tabarani (may Allah have mercy on him) said: "This hadith was narrated from al-Zuhri only by al-Nu'man; Marwan is alone in narrating it."
Hadith Referenceالمعجم الأوسط / باب العين / 4158
Hadith Gradingمحدثین:غريب، تفرد به مروان بن ثوبان ولم يُعرف
Hadith Takhrij«قال الطبراني: لم يروه عن الزهري إلا النعمان تفرد به مروان «الإعلام بسنته عليه الصلاة والسلام بشرح سنن ابن ماجه الإمام، ج 4، ص 84»» «قال الهيثمي: تفرد به مروان بن ثوبان قلت ولم أجد من ذكره «مجمع الزوائد ومنبع الفوائد، ج 1، ص 330»» «أخرجه الطبراني فى «الأوسط» برقم: 7524»