Sahih Al Bukhari – Book of Times Of The Prayers

Volumn 001, Book 010, Hadith Number 506.
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Narated By Abu Huraira RA : I heard Allah's Apostle PBUH 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 PBUH added, "That is the example of the five prayers with which Allah blots out (annuls) evil deeds."