Musannaf Ibn Abi Shayba 2:236

Abu Bakr narrated to us, he said: Abu Usama narrated to us, from al-A’mash, from Ibrahim, he said: Alqama and Abd al-Rahman ibn Abi Layla went out to their Bedouins. Ibrahim said: It used to please me that Abd al-Rahman ibn Abi Layla would command a son of his, a young boy, and he would perform the adhan.