Musnad Ahmad 5:393

Bahz and Abu Kamil said: Hammad narrated to us—Bahz said: Hisham ibn Amr al-Fazari informed us, from Abd al-Rahman ibn al-Harith ibn Hisham al-Makhzumi, from Ali, that the Messenger of Allah (peace and blessings of Allah be upon him) used to say at the end of his Witr: "O Allah, I seek refuge in Your pleasure from Your anger, and I seek refuge in Your pardon from Your punishment, and I seek refuge in You from You. I cannot enumerate Your praise; You are as You have praised Yourself."