Sahih Al Bukhari – Book of Good Manners And Form (Al-Adab)
Volumn 008, Book 073, Hadith Number 157.
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Narated By Malik : Similarly as above (156) adding, "Who believes in Allah and the Last Day should talk what is good or keep quiet." (i.e. abstain from dirty and evil talk, and should think before uttering).
Junaid Tahir