Narrated As-Saib bin Yazid:
In the life-time of the Prophet, Abu Bakr and Umar, the Adhan for the Jumua prayer used to be pronounced when the Imam sat on the pulpit. But during the Caliphate of 'Uthman when the Muslims increased in number, a third Adhan at Az-Zaura' was added. Abu 'Abdullah said, "Az-Zaura' is a place in the market of Medina."