Narrated `Abdullah bin `Amr: Abu Bakr As-Siddiq said to the Prophet (peace be upon him)
“O Allah’s Messenger (peace be upon him)! Teach me an invocation with which I may invoke Allah in my prayers.” The Prophet (peace be upon him) said, “Say: O Allah! I have wronged my soul very much (oppressed myself), and none forgives the sins but You; so please bestow Your Forgiveness upon me. No doubt, You are the Oft-Forgiving, Most Merciful.”
Sahih al-Bukhari, Vol. 9, Book 97, Hadith 17
