Musannaf Ibn Abi Shayba 3:1726

Abu Bakr narrated to us, he said: Hammad bin Abd al-Rahman narrated to us, from Zuhayr, from Imran bin Muslim, who said: Suwayd said: "If I were able, I would have given the adhan for them and led them in prayer." He said: So I mentioned that to Mus'ab bin Sa'd, and he said: "As for that, it is not from the Sunnah that one should be both the mu'adhdhin and the imam."