عَنِ ابْنِ عُمَرَ قَالَ: كَانَ الْمُسْلِمُونَ حِينَ قدمُوا الْمَدِينَة يَجْتَمعُونَ فيتحينون الصَّلَاة لَيْسَ يُنَادِي بِهَا أَحَدٌ فَتَكَلَّمُوا يَوْمًا فِي ذَلِكَ فَقَالَ بَعْضُهُمُ: اتَّخِذُوا مِثْلَ نَاقُوسِ النَّصَارَى وَقَالَ بَعْضُهُمْ: قَرْنًا مِثْلَ قَرْنِ الْيَهُودِ فَقَالَ عُمَرُ أَوَلَا تَبْعَثُونَ رَجُلًا يُنَادِي بِالصَّلَاةِ؟ فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «يَا بِلَالُ قُم فَنَادِ بِالصَّلَاةِ»

Ibn ‘Umar said that 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 one of them said, “Use something like the bell of the Christians." Another said, “Use a horn like that of the Jews." But when ‘Umar said, “I suggest that you send a man to announce the prayer," God’s Messenger said, “Get up, Bilal, and summon to prayer." (Bukhari and Muslim.)