Oneness, Uniqueness of Allah (Tawheed)

Bukhari :: Book 9 :: Volume 93 :: Hadith 625

Narrated Ibn Mas'ud:

A man asked the Prophet "What deeds are the best?" The Prophet said: (1) To perform the (daily compulsory) prayers at their (early) stated fixed times, (2) To be good and dutiful to one's own parents. (3) and to participate in Jihad in Allah's Cause."