Sahih Bukhari
Companions of the Prophet
Volume: 005 / Book Number: 057 / Hadith Number: 47
Narrated Ibn 'Umar:
During the lifetime of the Prophet we considered Abu Bakr as peerless and then 'Umar and then 'Uthman (coming next to him in superiority) and then we used not to differentiate between the companions of the Prophet