Sahih Bukhari Volume 8, Book 73, Hadith Number 47.

Narated By Abu Huraira : Allah’s Apostle said, “Anybody who believes in Allah and the Last Day should not harm his neighbor, and anybody who believes in Allah and the Last Day should entertain his guest generously and anybody who believes in Allah and the Last Day should talk what is good or keep quiet. (i.e. abstain from all kinds of evil and dirty talk).