Language:
كتاب الجمعة
11  
Friday Prayer
(24)
Chapter: To sit on the pulpit while Adhan is pronounced
(24)
باب الْجُلُوسِ عَلَى الْمِنْبَرِ عِنْدَ التَّأْذِينِ
Sahih al-Bukhari 915

Narrated As-Sa'ib bin Yazid I:

`Uthman bin `Affan introduced the second Adhan on Fridays when the number of the people in the mosque increased. Previously the Adhan on Fridays used to be pronounced only after the Imam had taken his seat (on the pulpit).

حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، أَنَّ السَّائِبَ بْنَ يَزِيدَ، أَخْبَرَهُ أَنَّ التَّأْذِينَ الثَّانِيَ يَوْمَ الْجُمُعَةِ أَمَرَ بِهِ عُثْمَانُ حِينَ كَثُرَ أَهْلُ الْمَسْجِدِ، وَكَانَ التَّأْذِينُ يَوْمَ الْجُمُعَةِ حِينَ يَجْلِسُ الإِمَامُ‏.‏
Reference : Sahih al-Bukhari 915
In-book reference : Book 11, Hadith 39
USC-MSA web (English) reference : Vol. 2, Book 13, Hadith 38
  (deprecated numbering scheme)