Musnad Ahmad 26:341

'Affan narrated to us, Shu'bah narrated to us, from Abu Ishaq, who said: I heard Abu 'Ubaydah, from his father, who said: The Prophet, peace and blessings of Allah be upon him, used to frequently say: "Glory be to You, O Allah, and with Your praise, O Allah, forgive me." When "When the victory of Allah has come and the conquest" was revealed, he said: "Glory be to You, O Allah, and with Your praise, O Allah, forgive me, for You are the Accepting of Repentance."