Musannaf Ibn Abi Shayba 1:1254

Abu Bakr narrated to us, he said: Abu Khalid al-Ahmar narrated to us, from 'Asim, from Abu 'Uthman, who said: We were sitting with 'Abdullah when the droppings of a sparrow fell upon him. He said: "Like this," and flicked it off with his hand.