The supplication that the Prophet of Allah ﷺ most often made was, "O Allah, forgive me for what I have done by mistake and what I have done deliberately, what I have hidden and what I have made known, what I have done in ignorance and what I have done intentionally."
حدثنا علي حدثنا معاذ حدثني أبي عن عون وهو العقيلي عن مطرف
كان عامة دعاء نبي الله ﷺ اللهم اغفر لي ما أخطأت وما تعمدت وما أسررت وما أعلنت وما جهلت وما تعمدت
Its isnad is sahih. Ali is Ibn Abdullah Madini, the peer of Ahmad, and he is one of the leading scholars of this field. Muaz is Ibn Hisham Dastawai, trustworthy, firmly established, and well known. Awn is Ibn Abu Shaddad, whom Ibn Main, Abu Dawud, and Ibn Hibban considered trustworthy, though some others judged him daif.The hadith was narrated by Bukhari, 11/196, no. 6398 (Fath), and Muslim, 2/534, no. 771, in the book on travelers, on supplication during night prayer.