Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
bukhari:603ʿImrān b. Maysarah > ʿAbd al-Wārith > Khālid al-Ḥadhhāʾ > Abū Qilābah > Anas > Dhakarūā al-Nār And al-Nnāqūs Fadhakarūā al-Yahūd Wa-al-Nnaṣārá Faʾumir Bilāl > Yashfaʿ al-Adhān

The people mentioned the fire and the bell (they suggested those as signals to indicate the starting of prayers), and by that they mentioned the Jews and the Christians. Then Bilal was ordered to pronounce Adhan for the prayer by saying its wordings twice, and for the Iqama (the call for the actual standing for the prayers in rows) by saying its wordings once. (Iqama is pronounced when the people are ready for the prayer).  

البخاري:٦٠٣حَدَّثَنَا عِمْرَانُ بْنُ مَيْسَرَةَ حَدَّثَنَا عَبْدُ الْوَارِثِ حَدَّثَنَا خَالِدٌ الْحَذَّاءُ عَنْ أَبِي قِلاَبَةَ عَنْ أَنَسٍ قَالَ

ذَكَرُوا النَّارَ وَالنَّاقُوسَ فَذَكَرُوا الْيَهُودَ وَالنَّصَارَى فَأُمِرَ بِلاَلٌ أَنْ يَشْفَعَ الأَذَانَ وَأَنْ يُوتِرَ الإِقَامَةَ  


See similar narrations below:

Collected by Bukhārī, Nasāʾī, Aḥmad, Nasāʾī's Kubrá
bukhari:606Muḥammad > ʿAbd al-Wahhāb > Khālid al-Ḥadhhāʾ > Abū Qilābah > Anas b. Mālik > Lammā Kathur al-Nās > Dhakarūā > Yaʿlamūā And Qt al-Ṣalāh Bishaʾ Yaʿrifūnah Fadhakarūā > Yūrūā Nār or Yaḍribūā Nāqūs Faʾumir Bilāl > Yashfaʿ al-Adhān

When the number of Muslims increased they discussed the question as to how to know the time for the prayer by some familiar means. Some suggested that a fire be lit (at the time of the prayer) and others put forward the proposal to ring the bell. Bilal was ordered to pronounce the wording of Adhan twice and of the Iqama once only.  

البخاري:٦٠٦حَدَّثَنَا مُحَمَّدٌ قَالَ أَخْبَرَنَا عَبْدُ الْوَهَّابِ قَالَ أَخْبَرَنَا خَالِدٌ الْحَذَّاءُ عَنْ أَبِي قِلاَبَةَ عَنْ أَنَسِ بْنِ مَالِكٍ قَالَ لَمَّا كَثُرَ النَّاسُ قَالَ ذَكَرُوا

أَنْ يَعْلَمُوا وَقْتَ الصَّلاَةِ بِشَىْءٍ يَعْرِفُونَهُ فَذَكَرُوا أَنْ يُورُوا نَارًا أَوْ يَضْرِبُوا نَاقُوسًا فَأُمِرَ بِلاَلٌ أَنْ يَشْفَعَ الأَذَانَ وَأَنْ يُوتِرَ الإِقَامَةَ  

bukhari:3457ʿImrān b. Maysarah > ʿAbd al-Wārith > Khālid > Abū Qilābah > Anas > Dhakarūā al-Nār And al-Nnāqūs Fadhakarūā al-Yahūd Wa-al-Nnaṣārá Faʾumir Bilāl > Yashfaʿ al-Adhān

The people mentioned the fire and the bell (as means proposed for announcing the time of prayer) and by such a suggestion they referred to the Jews and the Christians. But Bilal was ordered, "Pronounce the words of the Adhan (i.e. call for the prayer) twice and the Iqama once only."  

البخاري:٣٤٥٧حَدَّثَنَا عِمْرَانُ بْنُ مَيْسَرَةَ حَدَّثَنَا عَبْدُ الْوَارِثِ حَدَّثَنَا خَالِدٌ عَنْ أَبِي قِلاَبَةَ عَنْ أَنَسٍ ؓ قَالَ

ذَكَرُوا النَّارَ وَالنَّاقُوسَ فَذَكَرُوا الْيَهُودَ وَالنَّصَارَى فَأُمِرَ بِلاَلٌ أَنْ يَشْفَعَ الأَذَانَ وَأَنْ يُوتِرَ الإِقَامَةَ  

nasai:627Qutaybah b. Saʿīd > ʿAbd al-Wahhāb > Ayyūb > Abū Qilābah > Anas

"The Messenger of Allah ﷺ commanded Bilal to say the phrases of the Adhan twice and the phrases of the Iqamah once."  

النسائي:٦٢٧أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ قَالَ حَدَّثَنَا عَبْدُ الْوَهَّابِ عَنْ أَيُّوبَ عَنْ أَبِي قِلاَبَةَ عَنْ أَنَسٍ قَالَ

إِنَّ رَسُولَ اللَّهِ ﷺ أَمَرَ بِلاَلاً أَنْ يَشْفَعَ الأَذَانَ وَأَنْ يُوتِرَ الإِقَامَةَ  

ahmad:12001ʿAbd al-Wahhāb > Ayyūb > Abū Qilābah > Anas b. Mālik > Umir Bilāl

"Bilal was commanded to say the phrases of the Adhan twice and the phrases of the Iqamah once." (Using translation from Ibn Mājah 730)  

أحمد:١٢٠٠١حَدَّثَنَا عَبْدُ الْوَهَّابِ حَدَّثَنَا أَيُّوبُ عَنْ أَبِي قِلَابَةَ عَنْ أَنَسِ بْنِ مَالِكٍ قَالَ أُمِرَ بِلَالٌ

أَنْ يَشْفَعَ الْأَذَانَ وَيُوتِرَ الْإِقَامَةَ  

nasai-kubra:1604Qutaybah b. Saʿīd > ʿAbd al-Wahhāb > Ayyūb > Abū Qilābah > Anas

"The Messenger of Allah ﷺ commanded Bilal to say the phrases of the Adhan twice and the phrases of the Iqamah once." (Using translation from Nasāʾī 627)  

الكبرى للنسائي:١٦٠٤أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ قَالَ حَدَّثَنَا عَبْدُ الْوَهَّابِ عَنْ أَيُّوبَ عَنْ أَبِي قِلَابَةَ عَنْ أَنَسٍ

أَنَّ رَسُولَ اللهِ ﷺ «أَمَرَ بِلَالًا أَنْ يَشْفَعَ الْأَذَانَ وَأَنْ يُوتِرَ الْإِقَامَةَ»