Musnad Abu Ya'la al-Mawsili 156:6

Wahb ibn Baqiyyah narrated to us, Khalid narrated to us, from Yunus, from al-Hasan, from Abu Hurayrah, that the Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever takes from what Allah and His Messenger have obligated—a word, or two, or three, or four, or five—and ties them in the edge of his garment so that he may learn them." He (Abu Hurayrah) said: So I spread out my garment while the Messenger of Allah (may Allah bless him and grant him peace) was speaking, then I gathered it up. And I hope that I have not forgotten a single hadith of what the Messenger of Allah (may Allah bless him and grant him peace) said.