Musnad Ahmad 30:1290

Abu al-Nadr narrated to us, al-Mubarak narrated to us, from al-Hasan, from Abu Hurayrah, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Is there not a man who will take a word, or two, or three, or four, or five, from what Allah and His Messenger have ordained, and place them in the edge of his garment, so that he may learn them and teach them?" Abu Hurayrah said: I said, "I will, O Messenger of Allah." He said, "Spread out your garment." He said: So I spread out my garment, and the Messenger of Allah, peace and blessings of Allah be upon him, spoke, then said, "Gather it to yourself." So I gathered my garment to my chest. For I hope that I have not forgotten any hadith I heard from him after that.