It is narrated from Anas bin Malik (may Allah be pleased with him) that the first salab (slain man's gear) from which the khumus (one-fifth) was taken in Islam was the salab of al-Bara' bin Malik (may Allah be pleased with him). He had charged at the marzuban (a Persian governor), wounded him and then killed him, and his companions scattered away from him. Al-Bara' went down to him and took his belt and his bracelets. When he arrived, Umar bin al-Khattab (may Allah be pleased with him) walked over to Abu Talhah (may Allah be pleased with him) and said: O Abu Talhah, we do not take the khumus from the salab, but the salab of al-Bara' is (substantial) wealth, and I am going to take the khumus from it. So they valued the belt and the bracelets at thirty thousand.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12786