Jihad (Kitab Al-Jihad)
Dawud :: Book 14 : Hadith 2724
Narrated Umayr, client of AbulLahm:
I was present at Khaybar along with my masters who spoke about me to the Apostle of Allah (peace_be_upon_him). He ordered about me, and a sword was girded on me and I was trailing it. He was then informed that I was a slave. He, therefore, ordered that I should be given some inferior goods.