It is narrated from Sayyidah Aishah (may Allah be pleased with her) and Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) had two muezzins, Bilal and Ibn Umm Maktum (may Allah be pleased with them both). The Messenger of Allah (peace and blessings be upon him) said: "Bilal (may Allah be pleased with him) gives the adhan at night, so eat and drink until Ibn Umm Maktum gives the adhan." Al-Qasim said: There was no more between their two adhans than that this one would come down and that one would go up.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1790