In a long hadith, the Prophet ﷺ said between the tashahhud and the taslim, "Allah, forgive me for what I have done before and what I will do later, what I have concealed and what I have made known, what I have done in excess, and what You know better than I do. You are the One who brings forward and You are the One who delays. There is no god but You."
في حديث طويل يقول النبي ﷺ بين التشهد والتسليم: اللهم اغفر لي ما قدمت، وما أخرت، وما أسررت وما أعلنت وما أسرفت وما أنت أعلم به مني، أنت المقدم، وأنت المؤخر لا إله إلا أنت.
Muslim narrated it in "The Travelers" (771) through Yusuf Majishun, from his father, from Abdul-Rahman Araj, from Ubaydullah bin Abu Rafi, from Ali . See the hadith in full in the chapter on the opening supplication.