Musnad Ahmad 32:2117

'Affan narrated to us, Hammad narrated to us, Qatadah, Humayd, and Thabit informed us, from Anas, that some people from 'Uraynah came to Medina and found its climate unsuitable. The Messenger of Allah (peace and blessings of Allah be upon him) sent them to the camels of the charity and said: "Drink from their milk and their urine." They killed the shepherd of the Messenger of Allah (peace and blessings of Allah be upon him), drove away the camels, and apostatized from Islam. They were brought to the Messenger of Allah (peace and blessings of Allah be upon him), so he cut off their hands and feet from opposite sides, branded their eyes, and cast them into the Harrah. Anas said: "I used to see one of them biting the earth with his mouth until they died." And perhaps Hammad said: "Gnawing the earth with his mouth until they died."