The Prophet (ﷺ) used to supplicate: "Allahumm-aghfir li khati'ati, wajahli, wa israfi fi amri, wa ma Anta a'lamu bihi minni. Allahumm-aghfir li jiddi wa hazli, wa khata'i wa 'amdi, wa kullu dhalika 'indi. Allahumm-aghfir li ma qaddamtu wa ma akhkhartu, wa ma asrartu, wa ma a'lantu, wa ma Anta a'lamu bihi minni. Antal-Muqaddimu, wa Antal-Mu'akhkhiru; wa Anta 'ala kulli shai'in Qadir (O Allah! Forgive my errors, ignorance and immoderation in my affairs. You are better aware of my faults than myself. O Allah! Forgive my faults which I committed in seriousness or in fun deliberately or inadvertently. O Allah! Grant me pardon for those sins which I committed in the past and I may commit in future, which I committed in privacy or in public and all those sins of which You are better aware than me. You Alone can send whomever You will to Jannah, and You Alone can send whomever You will to Hell-fire and You are Omnipotent)."

[Al-Bukhari and Muslim].