Musannaf Ibn Abi Shayba 13:1678

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Al-Aswad ibn Shayban narrated to us, from Abu Nawfal ibn Abi Aqrab, from his father, who said: I found a purse (badrah), so I brought it to Umar ibn al-Khattab and said: "O Commander of the Faithful, relieve me of it." He said: "Bring it to the season (the Hajj season)." So I brought it to the season, and he said: "Announce it for a year." I announced it, but I did not find anyone who recognized it. I came to him and said: "Relieve me of it." He said: "Shall I not inform you of the best way to dispose of it? Give it in charity. If its owner comes and chooses the money, you shall pay it back to him, and the reward will be yours. And if he chooses the reward, then the reward is for him, and you have what you intended."