Musnad Ahmad 1153:487

Muhammad ibn Abdullah narrated to us, he said: Ayman ibn Nabil narrated to us, from Umm Kulthum, from Aisha, she said: When it was said to the Messenger of Allah, peace and blessings of Allah be upon him, that such-and-such person is in pain and does not eat food, he would say: "You must use Talbina, and feed it to him." He would say: "By the One in Whose hand is my soul, it washes the stomach of one of you just as one of you washes his face with water from dirt."