Musnad Ahmad 27:327

Waki’ narrated to us, Abu Janab narrated to us, from his father, from Ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no contagion, no superstition, and no owl (omen)." A man stood up to him and said: "O Messenger of Allah, what about a camel that has mange, and then the camels become mangy?" He said: "That is the decree. So who made the first one mangy?"