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.” (Sahih Al Bukhari Volume 1, Book 10, Hadith # 506)