Abu Bakr (RA) reported that he said to Allah's Messenger (ﷺ) : Teach me a supplication which I should recite in my prayer. Thereupon he (the Holy Prophet) said: Recite: "O Allah, I have done great wrong to myself." According to Qutaiba the words were: (much wrong) there is none to forgive the sins but Thou only, say: "Grant me pardon from Thyself, have mercy upon me for Thou art much Forgiving and Compassionate."
Hadith Referenceصحيح مسلم / كتاب الذكر والدعاء والتوبة والاستغفار / 2705
This hadith has been transmitted on the authority of 'Amr bin al-'As that Abu Bakr Siddiq (RA) said to Allah's Messenger (ﷺ) : Allah's Messenger, teach me a supplication which I should make in my prayer and in my house. The rest of the hadith is the same except with this variation that he said: Much wrong (Zulman Kathira).
Hadith Referenceصحيح مسلم / كتاب الذكر والدعاء والتوبة والاستغفار / 2705
'A'isha reported that Allah's Messenger (ﷺ) used to make these supplications: "O Allah, I seek refuge in Thee from the trial of Hell-Fire; and from the torment of Hell-Fire; and from the trial of the grave and torment of the grave; and from the evil of the trial of the affluence and from the evil of the trial of poverty and I seek refuge in Thee from the evil of the turmoil of the Dajjal. O Allah, wash away my sins with snow and hail water, purify my heart from the sins as is purified the white garment from the dirt, and keep away at a distance the sins from me as yawns the distance between the East and the West; O Allah, I seek refuge in Thee from sloth, from senility, from sin, and from debt."
Hadith Referenceصحيح مسلم / كتاب الذكر والدعاء والتوبة والاستغفار / 589