Musnad Ahmad 32:259

Waki’ narrated to us, Shu’bah narrated to us, from Abu al-Tayyah, who said: I heard Anas ibn Malik saying: The Messenger of Allah (peace and blessings of Allah be upon him) used to mingle with us, to the point that he would say to a small brother of mine: "O Abu ‘Umayr, what did the nughayr (a small bird) do?" — a bird he used to play with. He said: And he sprinkled water on a mat of ours. He said: Then he prayed upon it, and we lined up behind him.