Musannaf Ibn Abi Shayba 2:226

Abu Bakr narrated to us, he said: Yazid ibn Harun narrated to us, he said: A sheikh from the people of Basra narrated to us, he said: Al-Qasim ibn Awf al-Shaybani narrated to us, from Zayd ibn Arqam, he said: The Prophet (peace and blessings of Allah be upon him) said: "Bilal is the master of the mu'adhdhins (callers to prayer) on the Day of Resurrection, and none shall follow him except a believer." "And the mu'adhdhins will have the longest necks of all people on the Day of Resurrection."