Musannaf Ibn Abi Shayba 21:735

Abdullah ibn Idris narrated to us, from Isma'il, from Qays, who said: We entered upon Khabbab, and he had been cauterized with seven cauterizations in his stomach. He said: "Were it not that the Messenger of Allah (may Allah bless him and grant him peace) forbade us from praying for death, I would have prayed for it."