Sahih Bukhari
Times of the Prayers
Volume: 001 / Book Number: 010 / Hadith Number: 506
Narrated Abu Huraira:
I heard Allah's Apostle saying, "If there was a river at the door of anyone of you and he took a bath in it five times a day would you notice any dirt on him?" They said, "Not a trace of dirt would be left." The Prophet added, "That is the example of the five prayers with which Allah blots out (annuls) evil deeds."