It is narrated from Hazrat Abu Musa (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) used to supplicate with these prayers: O Allah! Forgive my sins and my ignorance, my exceeding the limits, and those (sins) which You know better than me. O Allah! Forgive all my sins, whether committed seriously or in jest, by mistake or deliberately; all of these are from me.
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 19738