"The third Adhan was ordered by 'Uthman when the number of people in Al-Madinah increased. The Messenger of Allah (ﷺ) only had one Adhan, and the Adhan on Friday was when the Imam sat down."
Sunan an-Nasa'i Book 14, Hadith 30
← Previous Hadith The first Adhan used to be when the Imam sat on the Minbar on Friday, at the time of the Messenger of Allah (ﷺ) and Abu Bakr and 'Umar. During the caliphate of 'Uthman, when the number of people increased, 'Uthman commanded that a third Adhan be given on Friday, so that Adhan was given from the top of Az-Zawra, and that is how it remained.

Sunan an-Nasa'i Book 14, Hadith 29 Next Hadith → "Bilal used to call the Adhan when the Messenger of Allah (ﷺ) sat on the Minbar on Friday, and when he came down he would say the Iqamah. It continued like that during the time of Abu Bakr and 'Umar, may Allah (SWT) be pleased with them."

Sunan an-Nasa'i Book 14, Hadith 31