Sahih Bukhari Volume 1, Book 10, Hadith 628

حَدَّثَنَا مُعَلَّى بْنُ أَسَدٍ، قَالَ حَدَّثَنَا وُهَيْبٌ، عَنْ أَيُّوبَ، عَنْ أَبِي قِلاَبَةَ، عَنْ مَالِكِ بْنِ الْحُوَيْرِثِ، أَتَيْتُ النَّبِيَّ صلى الله عليه وسلم فِي نَفَرٍ مِنْ قَوْمِي فَأَقَمْنَا عِنْدَهُ عِشْرِينَ لَيْلَةً، وَكَانَ رَحِيمًا رَفِيقًا، فَلَمَّا رَأَى شَوْقَنَا إِلَى أَهَالِينَا قَالَ ‏"‏ ارْجِعُوا فَكُونُوا فِيهِمْ وَعَلِّمُوهُمْ وَصَلُّوا، فَإِذَا حَضَرَتِ الصَّلاَةُ فَلْيُؤَذِّنْ لَكُمْ أَحَدُكُمْ وَلْيَؤُمَّكُمْ أَكْبَرُكُمْ ‏"‏‏

Narrated By Malik bin Huwairth : I came to the Prophet with some men from my tribe and stayed with him for twenty nights. He was kind and merciful to us. When he realized our longing for our families, he said to us, "Go back and stay with your families and teach them the religion, and offer the prayer and one of you should pronounce the Adhan for the prayer when its time is due and the oldest one amongst you should lead the prayer."