Musnad Ahmad 936:7

Abdullah narrated to us, Muhammad ibn Abi Bakr al-Muqaddami narrated to us, Abd al-Aziz ibn Muhammad al-Darawardi narrated to us, Umarah ibn Ghaziyyah narrated to us, from Salamah ibn Kuhayl, from Sa'sa'ah ibn Suhan, who said: He and a group with him arrived and found a whip. Its owner took it, and they neither commanded him nor forbade him. Then I came to Medina and met Ubayy ibn Ka'b and asked him. He said: "I found one hundred dinars during the time of the Prophet, may Allah bless him and grant him peace. He said: 'Announce it for a year.'" He repeated it to him until he mentioned three years. I said: "O Messenger of Allah?" He said: "It is yours."