Sahih Bukhari Volume 001, Book 002, Hadith Number 025.
Sahih Bukhari Book 02. Belief
Narated By Abu Huraira : Allah's Apostle was asked, "What is
the best deed?" He replied, "To believe in Allah and His
Apostle (Muhammad). The questioner then asked, "What is the
next (in goodness)? He replied, "To participate in Jihad
(religious fighting) in Allah's Cause." The questioner again
asked, "What is the next (in goodness)?" He replied, "To
perform Hajj (Pilgrim age to Mecca) 'Mubrur, (which is
accepted by Allah and is performed with the intention of
seeking Allah's pleasure only and not to show off and without
committing a sin and in accordance with the traditions of the
Prophet)."