From Sahih Muslim (Hadith 7004):
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)
Reference: Muslim 7004