Purification (Kitab Al-Taharah)
Dawud :: Book 1 : Hadith 44
Narrated AbuHurayrah:
The Prophet (peace_be_upon_him) said: The following verse was revealed in connection with the people of Quba': "In it are men who love to be purified" (ix.108). He (AbuHurayrah) said: They used to cleanse themselves with water after easing. So the verse was revealed in connection with them.