One day a companion was passing through a valley holding his merchandise on top of his camel. A thief came and put his sword to his neck and said I am going to kill you and take your merchandise. The companion asked him to allow him to make two rakat. In his sujood he made a dua to Allah to save him from the thief. Out of no where a warrior came and killed the thief. When the companion asked who he is, he said he is an angel.