One-fifth of Booty to the Cause of Allah (Khumus)

Bukhari :: Book 4 :: Volume 53 :: Hadith 347

Narrated Khaula Al-Ansariya:

I heard Allah's Apostle saying, "Some people spend Allah's Wealth (i.e. Muslim's wealth) in an unjust manner; such people will be put in the (Hell) Fire on the Day of Resurrection."