(22) باب الْمُؤَذِّنِ الْوَاحِدِ يَوْمَ الْجُمُعَةِ
Narrated As-Saib bin Yazid:
The person who increased the number of Adhans for the Jumua prayers to three was `Uthman bin
`Affan and it was when the number of the (Muslim) people of Medina had increased. In the lifetime of
the Prophet (ﷺ) there was only one Mu'adh-dhin and the Adhan used to be pronounced only after the
Imam had taken his seat (i.e. on the pulpit).
Reference: Sahih al-Bukhari 913
In-book reference: Book 11, Hadith 37
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 13, Hadith 36