Obligatory Charity Tax (Zakat)

Bukhari :: Book 2 :: Volume 24 :: Hadith 522

Narrated Abu Huraira :

The Prophet said, "Every day two angels come down from Heaven and one of them says, 'O Allah! Compensate every person who spends in Your Cause,' and the other (angel) says, 'O Allah! Destroy every miser.' "

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