Sahih Bukhari
Oneness, Uniqueness of Allah (Tawheed)
Volume: 009 / Book Number: 093 / Hadith Number: 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."