Musnad Abu Ya'la al-Mawsili 155:379

Al-Hasan ibn Hammad narrated to us, Mu'awiyah ibn Hisham narrated to us, from al-Walid ibn 'Abd Allah ibn Jami', from Abu al-Tufayl, from Abu Hurayrah, who said: I complained to the Messenger of Allah, peace and blessings of Allah be upon him, about poor memory. He said, "Spread out your cloak." He said: So I spread it out. He said, "Gather it up." He said: So I did not forget anything after that.