Sahih Bukhari Volume 7, Book 71, Hadith Number 615.

Narrated By Abu Huraira: Allah’s Apostle said, ‘There is no ‘Adha (no disease is conveyed from the sick to the healthy without Allah’s permission), nor Safar, nor Hama.” A Bedouin stood up and said, “Then what about my camels? They are like deer on the sand, but when a mangy camel comes and mixes with them, they all get infected with mangy.” The Prophet said, “Then who conveyed the (mange) disease to the first one?”