Mishkat al-Masabih #3829

He told that in the time of God's Messenger a horse of his went off and was taken by the enemy, but when the Muslims conquered them it was returned to him. A version says that after the death of the Prophet a slave of his ran away and joined himself to the Byzantines, and when the Muslims conquered them Khalid b. al-Walid returned him to him. Bukhari transmitted it.