A man kissed a woman (unlawfully), so he came to the Prophet (may Allah's peace and blessings be upon him) and told him of what he did. So Allah, the Almighty, revealed the verse: {And establish prayer at the two ends of the day and at the approach of the night. Indeed, good deeds do away with misdeeds.} [Sūrat Hūd: 114]

Ibn Mas‘ūd (may Allah be pleased with him) recounts an incident about a man from the Companions of the Prophet (may Allah's peace and blessings be upon him) who was called Abu al-Yusr. This man kissed a woman unlawfully then regretted what he did, so he went to the Prophet (may Allah's peace and blessings be upon him) and told him about it. Consequently Allah, the Exalted, revealed a verse that addressed his situation: {And establish prayer at the two ends of the day}, meaning perform the daytime prayers, which are Fajr, Zhuhr, and ‘Asr; {and at the approach of the night}, meaning perform as well the two evening prayers, which are Maghrib and ‘Ishā’; {Indeed, good deeds do away with misdeeds}, meaning that these five prayers are expiation for minor sins, such as the one that he had committed. So the man asked: "Is this for me only?", meaning if this expiation through prayer is specific to his case or applies to all people in general. The Prophet (may Allah's peace and blessings be upon him) replied: "This is for everybody of my Ummah, all of them" meaning that performing these five prayers is expiation for any Muslim who did something similar to what he had done. Abu al-Yusr himself narrated this story in detail. He said: "A woman came to me to buy some dates, so I told her that I had better quality dates at home. She came into the house with me and I approached her and kissed her. I later went to Abu Bakr and related this incident to him and his reply was for me to conceal my sin and ask Allah to forgive me without telling anyone. I was impatient so I went to ‘Umar and related it to him, and he told me to conceal my sin and ask Allah to forgive me without telling anyone. (Again) I was impatient so I went to the Messenger of Allah (may Allah's peace and blessings be upon him) and I told him what I had done. He said: 'Is this how you look after the wife of a man who has set out in the cause of Allah?' "At that moment Abu al-Yusr wished that he had just embraced Islam (because acceptance of Islam eliminates all previous sins). He was utterly desperate and started to believe that he must be from the people of the Hellfire. He continues his account: "The Prophet (may Allah's peace and blessings be upon him) then bowed his head down in silence for some time until Allah revealed to him the following verse: {And establish prayer at the two ends of the day and at the approach of the night. Indeed, good deeds do away with misdeeds. That is a reminder for those who remember} [Sūrat Hūd: 114]. The Messenger of Allah recited it to me, so his Companions asked him: 'O Messenger of Allah, is it (this verse) for this man in particular or for all people in general?' He replied: 'For all people in general.'" [At-Tirmidhi; classified as Hasan by Al-Albāni]
In another Hadīth, the Prophet (may Allah's peace and blessings be upon him) said: "There is not a Muslim who commits a sin, then he makes ablution and prays two Rak‘ahs, then asks Allah to forgive him for that sin, except that he will be forgiven." Then he recited these two verses: {And whoever does something wrong or wrongs himself but then seeks forgiveness of Allah will find Allah Forgiving and Merciful} [Sūrat An-Nisā’: 110], and: {And those who, when they commit an immorality or wrong themselves [by transgression], remember Allah and seek forgiveness for their sins - and who can forgive sins except Allah? - and they do not persist in what they have done while they know} [Sūrat Āl-‘Imrān: 135] [Ahmad; classified as Sahīh by Ahmad Shākir]. These revelations are certainly an indication of Allah's vast mercy upon His servants by making the five daily prayers and the voluntary prayers expiation for their sins. Otherwise everyone would be doomed (because of their many sins).