Sunan An-Nasai, Chapter: The Book of Purification

that some Bedouins from 'Urainah came to the Prophet (saw) and became Muslim, but the climate of Al-Madinah did not suit them; their skin turned yellow and their stomachs became swollen. The Messenger of Allah (saw) sent them to some pregnant camels of his and told them to drink their milk and urine until they recovered. Then they killed the camel-herder and drove the camels away. The Messenger of Allah (saw) sent people after them, and they were brought back. Their hands and feet were cut off and their eyes were smoldered with burning nails. The Commander of the Believers, Abdul-Malik, said to Anas - when he was narrating this Hadith to him - "(Were they being punished) for Kufr or for a sin?" He said: "For Kufr." (Sahih)