Abu Musa al-Ash‘ari told on the Prophet’s authority that he used to use this supplication:
“O God, forgive me my sin, my ignorance, my extravagance in my affairs, and what Thou knowest better than I do. O God, forgive me my serious and my frivolous sins, my unintentional and my intentional sins, for I am guilty of all that. O God, forgive me my former and my latter sins, what I have kept secret and what I have done openly, and what Thou knowest better than I do. Thou art the Advancer, Thou art the Delayer, and Thou art omnipotent.”
(Bukhari and Muslim.)