Hadith 368

نا بُنْدَارٌ ، حَدَّثَنَا عَبْدُ الْوَهَّابِ الثَّقَفِيُّ ، نا خَالِدٌ ، عَنْ أَبِي قِلابَةَ ، عَنْ أَنَسٍ ، قَالَ : " لَمَّا كَثُرَ النَّاسُ ذَكَرُوا أَنْ يَعْلَمُوا وَقْتَ الصَّلاةِ بِشَيْءٍ يَعْرِفُونَهُ ، فَذَكَرُوا أَنْ يُنَوِّرُوا نَارًا ، أَوْ يَضْرِبُوا نَاقُوسًا ، فَأُمِرَ بِلالٌ أَنْ يَشْفَعَ الأَذَانَ ، وَيُوتِرَ الإِقَامَةَ "
Sayyiduna Anas (may Allah be pleased with him) narrates that when the (Muslim) people increased in number, they discussed that there should be some well-known thing by which they could know the time of prayer (and gather for prayer). So they discussed that they could light a fire, or ring a bell. Then Sayyiduna Bilal (may Allah be pleased with him) was ordered to say the words of the adhan twice each, and the words of the iqamah once each.
Hadith Reference صحيح ابن خزيمه / جماع أبواب الأذان والإقامة / 368
Hadith Takhrij صحيح بخاري