Obligatory Charity Tax (Zakat)

Bukhari :: Book 2 :: Volume 24 :: Hadith 552

Narrated 'Umar:

Allah's Apostle used to give me something but I would say to him, "would you give it to a poorer and more needy one than l?" The Prophet (p.b.u.h) said to me, "Take it. If you are given something from this property, without asking for it or having greed for it take it; and if not given, do not run for it."