Musannaf Ibn Abi Shayba 3:1794

Waki’ narrated to us, he said: Sufyan narrated to us, from Mansur, from Hilal ibn Yasaf, and from Abu Abd al-Rahman—or Hilal—from Sa’d ibn Ubaydah, from Abu Abd al-Rahman, he said: Ali said: The mu'adhdhin has more authority over the adhan, and the imam has more authority over the iqamah.