Ibn 'Abbas (May Allah be pleased with them) reported

The Messenger of Allah (ﷺ) used to supplicate: "Allahumma laka aslamtu, wa bika amantu, wa 'alaika tawakkaltu, wa ilaika anabtu, wa bika khasamtu, wa ilaika hakamtu. Faghfir li ma qaddamtu, wa ma akh-khartu, wa ma asrartu wa ma a'lantu, Antal-Muqaddimu, wa Antal-Mu'akhkhiru, la ilaha illa Anta (O Allah! to You I submit, in You I affirm my faith, in You I repose my trust, to You I turn in repentance and with Your Help I contend my adversaries and from You I seek judgement. O Allah! Grant me forgiveness for the faults which I made in past and those ones I may commit in the future, those which I committed secretly or openly. You Alone send whomever You will to Jannah, and You Alone send whomever You will to Hell-fire. There is none worthy of worship except You)." Another narration adds: "La hawla wa la quwwata illa billah (There is no strength to resist evil and no power to do good except through Allah)."

[Al-Bukhari and Muslim].