Sahih Bukhari Volume 007, Book 071, Hadith Number 667.
Narrated By Abu Huraira : Allah's Apostle said, "No 'Adha." Abu Huraira also said: The Prophet said, "The cattle suffering from a disease should not be mixed up with healthy cattle (or said "Do not put a patient with a healthy person as a precaution.") Abu Huraira also said: Allah's Apostle said, "No 'Adha." A Bedouin got up and said, "Don't you see how camels on the sand look like deer but when a mangy camel mixes with them, they all get infected with mange?" On that the Prophet said, "Then who conveyed the (mange) disease to the first camel?"