Pilgrimmage (Hajj)
Bukhari :: Book 2 :: Volume 26 :: Hadith 719
Narrated 'Abdullah bin Masud:
I offered (only a) two Rakat prayer with the Prophet (at Mina), and similarly with Abu Bakr and with 'Umar, and then you d offered in opinions. Wish that I would be lucky enough to have two of the four Rakat accepted (by Allah).