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

Bukhari :: Book 4 :: Volume 53 :: Hadith 376

Narrated Jubair bin Mutim:

That while he was with Allah's Apostle who was accompanied by the people on their way back from Hunain, the bedouins started begging things of Allah's Apostle so much so that they forced him to go under a Samura tree where his loose outer garment was snatched away. On that, Allah's Apostle stood up and said to them, "Return my garment to me. If I had as many camels as these trees, I would have distributed them amongst you; and you will not find me a miser or a liar or a coward."