Sahih Bukhari
Sahih Bukhari Volume 005, Book 057, Hadith Number 110.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 57. Companions of the Prophets
Narated By Humran bin Abbas : Muawiya said (to the people), "You offer a prayer which we, who were the companions of the Prophet never saw the Prophet offering, and he forbade its offering," i.e. the two Rakat after the compulsory 'Asr prayer.