Sahih Muslim Book 4, Hadith Number 741.
Chapter : How Adhan is to be pronounced.
Ibn Umar reported: The Messenger of Allah (may peace be upon him) had two Mu’adhdhins, Bilal and ‘Abdullah b. Umm Maktum, who (latter) was blind.
Ibn Umar reported: The Messenger of Allah (may peace be upon him) had two Mu’adhdhins, Bilal and ‘Abdullah b. Umm Maktum, who (latter) was blind.