One-fifth of Booty to the Cause of Allah (Khumus)
Bukhari :: Book 4 :: Volume 53 :: Hadith 360
Narrated Marwan bin Al-Hakim and Miswar bin Makhrama:
When the Hawazin delegation came to Allah's Apostle after they had embraced Islam and requested him to return their properties and war prisoners to them, Allah's Apostle said, "To me the best talk is the truest, so you may choose either of two things; the war prisoners or the wealth, for I have delayed their distribution." Allah's Apostle had waited for them for over ten days when he returned from Ta'if. So, when those people came to know that Allah's Apostle was not going to return to them except one of the two things the said, "We choose our war Prisoners 'Allah's Apostle stood up amongst the Muslims, and after glorifying Allah as He deserved, he said, "Now then, these brothers of yours have come to us with repentance, and I see it logical that I should return their captives to them, so whoever of you likes to do that as a favor then he can do it, and whoever amongst you likes to stick to his share, let him give up his prisoners and we will compensate him from the very first Fai' (i.e. war booty received without fight) which Allah will give us." On that, all the people said. 'O Allah's Apostles We have agreed willingly to do so (return the captives)" Then Allah's Apostle said to them "I do not know who amongst you has agreed to this and who has not. You should return and let your leaders inform me of your agreement." The people returned and their leaders spoke to them, and then came to Allah's Apostle and said, "All the people have agreed willingly to do so and have given the permission to return the war prisoners (without Compensation)" (Az-Zuhri, the sub-narrator states) This is what has been related to us about the captives of Hawazin.