The Messenger of Allah ﷺ said that the verse "In it are men who love to purify themselves, and Allah loves those who purify themselves" [Tawbah 9:108] was revealed concerning the people of Quba. He said they used to clean themselves with water after relieving themselves, so this verse was revealed about them.
حدثنا أبو كريب حدثنا معاوية بن هشام عن يونس بن الحارث عن إبراهيم بن أبي ميمونة عن أبي صالح
قال رسول الله ﷺ نزلت في أهل قباء {فيه رجال يحبون أن يتطهروا والله يحب المطهرين} قال كانوا يستنجون بالماء فنزلت فيهم هذه الآية
[Hasan] Abu Dawud narrated it in "Purification," chapter "On Cleansing with Water," no. 44, and Tirmidhi narrated it and said, "Gharib." Yunus is daif, and his teacher is of unknown status, but the preceding hadith (355) serves as a corroborating witness for it.