Musannaf Ibn Abi Shayba 2:224

Abu Bakr narrated to us, he said: Ya'la ibn 'Ubayd narrated to us, from Talha ibn Yahya, he said: I heard Mu'awiyah saying: I heard the Prophet, may Allah bless him and grant him peace, saying: "Indeed, the callers to prayer (mu'adhdhins) will have the longest necks of all people on the Day of Resurrection."