Zakat (Kitab Al-Zakat)
Dawud :: Book 9 : Hadith 1645
Narrated Malik ibn Nadlah:
The Prophet (peace_be_upon_him) said: Hands are of three types: Allah's hand is the upper one; the bestower's hand is the one near it; the beggar's hand is the lower one. So bestow what is surplus, and do not submit yourself to the demand of your soul.