Sunan Abi Dawud 1509
سنن أبي داود#1509SahihAli b. Abi Talib said:When the Prophet (ﷺ) uttered 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 You know better than I do. You are the Advancer, the Delayer, there is no god but You
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih
In-book reference: 8:94