Musnad Ahmad 32:1036

Bahz narrated to us, Muthanna ibn Sa'id narrated to me, from Abu al-Tayyah, from Anas, who said: The Prophet, peace and blessings of Allah be upon him, used to visit Umm Sulaym, and she had a small son who was called Abu Umayr. The Prophet, peace and blessings of Allah be upon him, used to say: "O Abu Umayr, what did the nughayr (small bird) do?" He said: A small bird he used to play with. And the Messenger of Allah, peace and blessings of Allah be upon him, used to visit Umm Sulaym sometimes and speak with her. Then the prayer would overtake him, so he would pray on a rug, which was a mat that he would sprinkle with water.