Musannaf Ibn Abi Shaybah

Hazrat Sa’ib bin Yazid says that the Messenger of Allah (peace and blessings be upon him) had only one muezzin, who would call the adhan when the Prophet (peace and blessings be upon him) sat on the pulpit, and would say the iqamah when the Prophet (peace and blessings be upon him) descended from the pulpit. The same practice was followed during the time of Hazrat Abu Bakr and Hazrat Umar. When the era of Hazrat Uthman came, the people increased in number and spread out, so he added a third adhan at the time of midday.