From Sahih Bukhari (Hadith 617):
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
Reference: Bukhari 617