Friday Prayer

Bukhari :: Book 2 :: Volume 13 :: Hadith 38

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).

Source materials are from the University of Southern California MSA site
Hadith eBooks converted from Imaan Star