Musnad Ahmad 1012:100

Abu al-Mughirah narrated to us, Bishr ibn Abdullah—meaning Ibn Yasar al-Sulami—narrated to us, he said: Ubadah ibn Nasi narrated to me, from Junadah ibn Abi Umayyah, from Ubadah ibn al-Samit, who said: The Messenger of Allah (peace and blessings of Allah be upon him) used to be occupied. When a migrating man would come to the Messenger of Allah (peace and blessings of Allah be upon him), he would entrust him to a man among us to teach him the Quran. The Messenger of Allah (peace and blessings of Allah be upon him) entrusted a man to me. He was with me in the house, and I would feed him the dinner of the household, and I would teach him the Quran. Then he departed to his family, and he felt that he owed me a right, so he gifted me a bow, the wood of which I had never seen better, nor had I seen one with a more beautiful curve. I came to the Messenger of Allah (peace and blessings of Allah be upon him) and said: "What do you see regarding it, O Messenger of Allah?" He said: "A coal between your shoulder blades that you have hung around your neck," or "that you have suspended."