Musnad Ahmad 25:1080

Husayn ibn Ali narrated to us, from Za'idah, from Simak, from Ikrimah, from Ibn Abbas, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) would have a slave girl bring him a shoulder [of meat] from the cooking pot, and he would eat from it. Then he would go out to the prayer and pray, and he did not perform ablution, nor did he touch water."