It is narrated from Sayyidah Aisha (may Allah be pleased with her) that the Noble Prophet (peace and blessings be upon him) had two muezzins: Bilal and the son of Umm Maktum. So the Messenger of Allah (peace and blessings be upon him) said: "Bilal gives the call to prayer during the night, so keep eating and drinking until you hear the call to prayer of Ibn Umm Maktum." Qasim said: There was such an interval between their calls to prayer that one would descend and the other would ascend (for the call to prayer).
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1224
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):حديث ابن عمر متفق عليه، [مكتبه الشامله نمبر: 1227]
Hadith Takhrijیہ حدیث صحیح ہے۔ دیکھئے: [بخاري 622] ، [مسلم 1092/38] و [صحيح ابن حبان 3473]
Brief Explanation
(Commentary on Ahadith 1223 to 1224)
During the era of the Messenger (sallallahu alayhi wa sallam), it was customary that the adhan (call to prayer) for sahur (pre-dawn meal) or tahajjud (late night prayer) was given by Sayyiduna Bilal (radi Allahu anhu), and the adhan for Fajr (dawn prayer) was given by Sayyiduna Abdullah ibn Umm Maktum (radi Allahu anhu).
This same practice continued during the era of the Caliphate and has remained in effect up to the present day. Therefore, this is clear evidence for the adhan of sahur and tahajjud.