Musannaf Ibn Abi Shayba 33:1132

Waki’ narrated to us, from Isra’il, from Abu Ishaq, from Abu ‘Ubaydah, that a tyrant from among the tyrants said: "I will not cease until I look at the One who is in the heaven." He said: So Allah empowered against him the weakest of His creation, and a gnat entered his nose, and death seized him. He said: "Strike my head." So they struck it until they scattered his brain.