Sahih Bukhari
Sahih Bukhari Volume 003, Book 048, Hadith Number 824.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 48. Witnesses
Narated By Abdullah bin Umar : The Prophet said, "Bilal pronounces the Adhan when it is still night (before dawn), so eat and drink till the next Adhan is pronounced (or till you hear Ibn Um Maktum's Adhan)." Ibn Um Maktum was a blind man who would not pronounce the Adhan till he was told that it was dawn.