Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 1405
Narated By Ali ibn Abu Talib : When the Prophet (pbuh) uttered the salutation at the end of the prayer, he used to say: "O Allah, forgive me my former and latter sins, what I have kept secret and what I have done openly, and what I have done extravagance; and what Thou knowest better than I do. Thou art the Advancer, the Delayer, there is no god but Thou"