Musnad Ahmad 435:71

Ibn Numayr narrated to us, Talhah ibn Yahya narrated to us, from Isa ibn Talhah, who said: I heard Muawiyah say, when the muezzin came to him to inform him of the prayer: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Indeed, the muezzins will have the longest necks of all people on the Day of Resurrection."