Hadith.2487 - The Messenger of Allah سبحانه وتعالى (peace and blessings of Allah سبحانه وتعالى be upon him and his family) forbade stepping over the camel line (caravan).
It was asked: "O Messenger of Allah سبحانه وتعالى, why?"
Prophet صلى الله عليه وعلى آله وسلم replied: "Because there is not a single camel line except that between one camel and the next there is a devil."