Oneness, Uniqueness of Allah (Tawheed)

Bukhari :: Book 9 :: Volume 93 :: Hadith 568

Narrated Abu Musa:

Whenever a beggar or a person in need of something came to the Prophet , he used to say (to his companions), "Intercede (for him) and you will be rewarded for that, and Allah will fulfill what He will through His Apostle's tongue."