Ibn Mas'ud narrated:
The Messenger of Allah (s.a.w) stood among us and said: 'One thing does not infect another.' So a Bedouin said: 'O Messenger of Allah! If a camel gets mangy glands and we leave it at the resting place of camels, then all of the camels get mange?' The Messenger of Allah (s.a.w) said: 'Who caused the first to get manage? There is no 'Adwa nor safar. Allah created every soul, so he wrote its life, its provision, and its afflictions.'