Sahih Muslim, Chapter: Faith (Kitab Al Iman)

We went to Khaibar along with the Apostle (may peace be upon him) and Allah granted us victory. We plundered neither gold nor silver but laid our hands on goods, corn and clothes, and then bent our stops to a valley; along with the Messenger of Allah (may peace be upon him) there was a slave who was presented to him by one Rifa'a b. Zaid of the family of Judham, a tribe of Dubayb. When we got down into the valley the slave of the Messenger of Allah stood up and began to unpack the saddle-bag and was suddenly struck by a (stray) arrow which proved fatal. We said: There is a greeting for him, Messenger of Allah, as he is a martyr. Upon this the Messenger of Allah (may peace be upon him) remarked: Nay, not so. By Him in Whose hand is the life of Muhammad, the small garment which he stole from the booty on the day of Khaibar but which did not (legitimately) fall to his lot is burning like the Fire (of Hell) on him. The people were greatly perturbed (on hearing this). A person came there with a lace or two laces and said: Messenger of Allah, I found (them) on the day of Khaibar. He (the Holy Prophet) remarked: This is a lace of fire or two laces of fire.