Sahih Muslim Book 35, Hadith Number 6563.
Chapter : Refuge from the evil of what one has done, and what one has not done.
Abu Musa Ash’ari reported on the authority of his father that Allah’s Apostle (may peace be upon him) used to supplicate in these words: “O Allah, forgive me my faults, my ignorance, my immoderation in my concerns. And Thou art better aware (of my affairs) than myself. O Allah, grant me forgiveness (of the faults which I committed) seriously or otherwise (and which I committed inadvertently and deliberately. All these (failings) are in me. O Allah, grant me forgiveness from the fault which I did in haste or deferred, which I committed in privacy or in public and Thou art better aware of (them) than myself. Thou art the First and the Last and over all things Thou art Omnipotent.”