كتاب التوبة
50  
The Book of Repentance
(7)
Chapter: The Words Of Allah The Most High: "Verily, The Good Deeds Remove The Evil Deeds"
(7)
Sahih Muslim 2763 b

Ibn Mas'ud reported that a person came to Allah's Messenger (ﷺ) and told him that he had kissed a woman or touched her with his hand or did something like this. He inquired of him about its expiation. It was (on this occasion) that Allah, the Exalted and Glorious, revealed this verse (as mentioned above).

حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، حَدَّثَنَا الْمُعْتَمِرُ، عَنْ أَبِيهِ، حَدَّثَنَا أَبُو عُثْمَانَ، عَنِ ابْنِ، مَسْعُودٍ أَنَّ رَجُلاً، أَتَى النَّبِيَّ صلى الله عليه وسلم فَذَكَرَ أَنَّهُ أَصَابَ مِنِ امْرَأَةٍ إِمَّا قُبْلَةً أَوْ مَسًّا بِيَدٍ أَوْ شَيْئًا كَأَنَّهُ يَسْأَلُ عَنْ كَفَّارَتِهَا - قَالَ - فَأَنْزَلَ اللَّهُ عَزَّ وَجَلَّ ‏.‏ ثُمَّ ذَكَرَ بِمِثْلِ حَدِيثِ يَزِيدَ ‏.‏
Reference : Sahih Muslim 2763b
In-book reference : Book 50, Hadith 48
USC-MSA web (English) reference : Book 37, Hadith 6656
  (deprecated numbering scheme)