Musannaf Ibn Abi Shayba 1:550

Ibn Numayr narrated to us, he said: Uthman ibn Hakim narrated to us, from al-Zuhri, from Abu Sufyan ibn Sa’id ibn al-Mughirah ibn al-Akhnas, that he entered upon his maternal aunt, Umm Habibah. She gave him a drink of *sawiq* (roasted barley flour drink) to drink. Then she said: "O son of my sister, perform ablution, for I heard the Messenger of Allah, may Allah bless him and grant him peace, say: 'Perform ablution from what the fire has touched.'"