It is narrated from Sayyiduna Malik bin al-Huwayrith (may Allah be pleased with him) that we came to the Messenger of Allah (peace and blessings be upon him), and we were all young men of about the same age. We stayed with him for twenty nights. The Messenger of Allah (peace and blessings be upon him) was very gentle and merciful. He thought that we had come to long for our families, and he asked us about those we had left behind among our families, and we told him. He (peace and blessings be upon him) said: "Go back to your families, stay among them, teach them (the religion) and command them (with it). When the time for prayer comes, let one of you call the adhan, and then let the eldest of you lead the prayer."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2269