Musannaf Ibn Abi Shayba 1:551

Khalid ibn Makhlad narrated to us, he said: Abd al-Rahman ibn Abd al-Aziz al-Ansari narrated to us, he said: Al-Zuhri narrated to me, he said: Abu Salamah ibn Abd al-Rahman ibn Awf narrated to me, he said: Abu Sufyan ibn Sa'id al-Akhnasi informed me, he said: I entered upon my maternal aunt, Umm Habibah, and she gave me *sawiq* (barley meal) 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 fire has touched.'"