Ibn Umar reported: When the Muslims came to Medina, they gathered and sought to know the time of prayer but no one summoned them. One day they discussed the matter, and some of them said, “Use something like the bell of the Christians,” and some of them said, “Use horn like that of the Jews.” Umar said, “Why not send a man to call people to prayer?” The Messenger of Allah, peace and blessings be upon him, said, “O Bilal, get up and summon the people to prayer.”

Source: Sahih Bukhari 579, Sahih Muslim 377

Grade: Muttafaqun Alayhi (authenticity agreed upon) according to Al-Bukhari and Muslim

عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ أَنَّهُ قَالَ كَانَ الْمُسْلِمُونَ حِينَ قَدِمُوا الْمَدِينَةَ يَجْتَمِعُونَ فَيَتَحَيَّنُونَ الصَّلَوَاتِ وَلَيْسَ يُنَادِي بِهَا أَحَدٌ فَتَكَلَّمُوا يَوْمًا فِي ذَلِكَ فَقَالَ بَعْضُهُمْ اتَّخِذُوا نَاقُوسًا مِثْلَ نَاقُوسِ النَّصَارَى وَقَالَ بَعْضُهُمْ قَرْنًا مِثْلَ قَرْنِ الْيَهُودِ فَقَالَ عُمَرُ أَوَلَا تَبْعَثُونَ رَجُلًا يُنَادِي بِالصَّلَاةِ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَا بِلَالُ قُمْ فَنَادِ بِالصَّلَاةِ

579 صحيح البخاري كِتَاب الْأَذَانِ فأمر بلال أن يشفع الأذان وأن يوتر الإقامة

377 صحيح مسلم كِتَاب الصَّلَاةِ بَاب بَدْءِ الْأَذَانِ