Musannaf Ibn Abi Shayba 1:549

Ibn ‘Ulayyah narrated to us, from Ma’mar, from al-Zuhri, from ‘Umar ibn ‘Abd al-‘Aziz, from Ibrahim ibn ‘Abd Allah ibn Qāriz, that Abu Hurayrah ate pieces of dried yogurt (aqt). Then he stood up and performed ablution. He said: "Do you know why I performed ablution? I ate pieces of dried yogurt, and I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'Perform ablution from what the fire has touched.'" He said: And ‘Umar used to perform ablution from [eating] sugar.