Allah's Messenger (ﷺ) said, 'There is no 'Adwa (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 (ﷺ) said, "Then who conveyed the (mange) disease to the first
one?"
Sahih al-Bukhari Book 76, Hadith 34