Volume 9 · Book 91 · Hadith 354
Narrated 'Abdullah bin 'Umar: The Prophet said, "Bilal pronounces the Adhan at night so that you may eat and drink till Ibn Um Maktum pronounces the Adhan (for the Fajr prayer)."
— Sahih Bukhari, Volume 9, Book 91: Accepting Information Given by a Truthful Person, Hadith #354