As-Sa'ib bin Yazid narrated that: 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.

As-Sa'ib bin Yazid narrated that: 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.

أَخْبَرَنَا مُحَمَّدُ بْنُ سَلَمَةَ، قَالَ حَدَّثَنَا ابْنُ وَهْبٍ، عَنْ يُونُسَ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي السَّائِبُ بْنُ يَزِيدَ، أَنَّ الأَذَانَ، كَانَ أَوَّلُ حِينَ يَجْلِسُ الإِمَامُ عَلَى الْمِنْبَرِ يَوْمَ الْجُمُعَةَ فِي عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم وَأَبِي بَكْرٍ وَعُمَرَ فَلَمَّا كَانَ فِي خِلاَفَةِ عُثْمَانَ وَكَثُرَ النَّاسُ أَمَرَ عُثْمَانُ يَوْمَ الْجُمُعَةِ بِالأَذَانِ الثَّالِثِ فَأُذِّنَ بِهِ عَلَى الزَّوْرَاءِ فَثَبَتَ الأَمْرُ عَلَى ذَلِكَ ‏.‏