‏البيوع : Hadeeth No:3632 Anas b. Malik (Allaah be pleased with him) reported: We were forbidden that a townsman should sell for a man of the desert, even if he is his brother or father....

‏الجهاد والسير‏ : Hadeeth No:4470 The (foregoing) tradition has also been narrated on the authority of Hatim through the same chain of transmitters with the difference that according to this version both these types of expeditions were seven in number....