Musnad Ahmad 1012:126

'Abdullah narrated to us, Shuja' ibn Makhlad narrated to us, Hushaym narrated to us, from Mughirah, from al-Sha'bi, who said: 'Ubadah ibn al-Samit said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whoever sustains a wound on his body, then gives it as charity, Allah will expiate for him the like of what he gave as charity."