Sayyiduna Abdullah bin Umar (may Allah be pleased with them) narrated that the Messenger of Allah (peace and blessings of Allah be upon him) said: Bilal (may Allah be pleased with him) gives the call to prayer during the night, so you may continue eating and drinking until Ibn Umm Maktum gives the call to prayer.
Hadith Referenceاللؤلؤ والمرجان / كتاب الصيام / 662
Hadith Gradingمحدثین:«صحیح»
Hadith Takhrij«صحیح، أخرجه البخاري في: 10 كتاب الأذان: 11 باب أذان الأعمى إذا كان له من يخبره»
Brief Explanation
During the era of the Messenger (sallallahu alayhi wa sallam), it was the established practice that the call to prayer (adhan) for the pre-dawn meal (suhur) was given by Sayyiduna Bilal (radi Allahu anhu), and the call to prayer for the dawn (fajr) prayer was given by Sayyiduna Abdullah bin Umm Maktum (radi Allahu anhu). This method continued during the era of the Caliphate as well, and this practice has remained in place in Madinah Munawwarah up to the present day. Those who oppose the adhan for suhur are mistaken in their view. The purpose of this adhan is not only to awaken people for the pre-dawn meal (suhur), but also to awaken them for the night prayer (tahajjud). (Raaz)