Musnad Ahmad 129:1

Isma'il ibn Ibrahim narrated to us, Ayyub narrated to us, from Abu Qilabah, from Malik ibn al-Huwayrith, who said: We came to the Messenger of Allah, may Allah bless him and grant him peace, and we were youths of similar age. We stayed with him for twenty nights. He said: The Messenger of Allah, may Allah bless him and grant him peace, was merciful and gentle. He thought that we had longed for our families, so he asked us about whom we had left behind among our families, and we informed him. He said: "Return to your families, and stay among them, and teach them, and command them. When the prayer time arrives, let one of you call the adhan for you, then let the oldest of you lead you in prayer."