Sahih Bukhari Volume 001, Book 010, Hadith Number 505.
Narated By 'Abdullah : I asked the Prophet "Which deed is the dearest to Allah?" He replied, "To offer the prayers at their early stated fixed times." I asked, "What is the next (in goodness)?" He replied, "To be good and dutiful to your parents" I again asked, "What is the next (in goodness)?" He replied, 'To participate in Jihad (religious fighting) in Allah's cause." 'Abdullah added, "I asked only that much and if I had asked more, the Prophet would have told me more."