We came to the Messenger of Allah ﷺ and we were all young men of nearly equal age. We stayed with him (the Holy Prophet) for twenty nights, and as the Messenger of Allah ﷺ was extremely kind and tender of heart, he therefore, thought that we were eager (to see) our family (we felt homesick). So he asked us about the members of the family that we had left behind and when we informed him, he said: Go back to your family, stay with them, and teach them (beliefs and practices of Islam) and exhort them to good, and when the time for prayer comes, one amongst you should announce Adhan and then the oldest among you should lead the prayer. (Using translation from Muslim 674a)  

أَتَيْنَا رَسُولَ اللهِ ﷺ وَنَحْنُ شَبَبَةٌ مُتَقَارِبُونَ فَأَقَمْنَا عِنْدَهُ عِشْرِينَ لَيْلَةً قَالَ وَكَانَ رَسُولُ اللهِ ﷺ رَحِيمًا رَفِيقًا فَظَنَّ أَنْ قَدِ اشْتَقْنَا إِلَى أَهْلِنَا وَسَأَلْنَا عَمَّنْ تَرَكْنَا مِنْ أَهْلِنَا فَأَخْبَرْنَاهُ فَقَالَ «ارْجِعُوا إِلَى أَهْلِيكُمْ فَأَقِيمُوا عِنْدَهُمْ وَعَلِّمُوهُمْ وَمُرُوهُمْ إِذَا حَضَرَتِ الصَّلَاةُ فَلْيُؤَذِّنْ لَكُمْ أَحَدُكُمْ وَلْيَؤُمَّكُمْ أَكْبَرُكُمْ»  

"Abu Qilabah said to me (Ayyub): He ('Amr) is still alive, do you want to meet him?" I met him and asked him, and he said: "When Makkah was conquered, all the people hastened to announce their Islam. My father went to announce the Islam of the poeple of our village, and when he came back we went to see him and he said: 'By Allah, I have indeed come to you from the Messenger of Allah ﷺ'. He said: 'Pray such and such a prayer at such and such a time, pray such and such a prayer at such and such a time. When the time for prayer comes let one of you call the Adhan and let the one who knows the most Qur'an lead the prayer.'" (Using translation from Nasāʾī 636)   

لَمَّا كَانَتْ وَقْعَةُ الْفَتْحِ بَادَرَ كُلُّ قَوْمٍ بِإِسْلَامِهِم فَذَهَبَ أَبِي بِإِسْلَامِ أَهْلِ حَوَائِنَا فَلَمَّا قَدِمَ اسْتَقْبَلْنَاهُ فَقَالَ جِئْتُكُمْ وَاللهِ مِنْ عِنْدِ رَسُولِ اللهِ ﷺ حَقًّا فَقَالَ «صَلُّوا صَلَاةَ كَذَا فِي حِينِ كَذَا وَصَلُّوا صَلَاةَ كَذَا فِي حِينِ كَذَا فَإِذَا حَضَرَتِ الصَّلَاةُ فَلْيُؤَذِّنْ لَكُمْ أَحَدُكُمْ وَلْيَؤُمَّكُمْ أَكْثَرُكُمْ قُرْآنًا»