Musnad Ahmad 1153:2032

Rawh narrated to us, Ayman ibn Nabil narrated to us, he said: Fatimah bint Abi Layth narrated to me, from Umm Kulthum bint ‘Amr ibn Abi ‘Aqrab, she said: I heard ‘Aishah saying: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "You must use *at-talbinah* (barley porridge), the disliked yet beneficial. 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 from dirt with water." And she said: When someone from her family would complain of an ailment, the pot would not cease to be on the fire until one of the two ends came upon it (i.e., until the person either recovered or passed away). And he (Rawh) said, meaning in Baghdad: When anyone from his family would complain of something, the pot would not cease...