Sahih Bukhari
Call to Prayers (Adhaan)
Volume: 001 / Book Number: 011 / Hadith Number: 591
Narrated Salim bin Abdullah:
My father said that Allah s Apostle said, "Bilal pronounces 'Adhan at night, so keep on eating and drinking (Suhur) till Ibn Um Maktum pronounces Adhan." Salim added, "He was a blind man who would not pronounce the Adhan unless he was told that the day had dawned."