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

Bukhari :: Book 4 :: Volume 53 :: Hadith 410

Narrated Anas:

The Prophet said, ''Every betrayer will have a flag on the Day of Resurrection" One of the two sub-narrators said that the flag would be fixed, and the other said that it would be shown on the Day of Resurrection, so that the betrayer might be recognized by it.