Good Manners and Form (Al-Adab)
Bukhari :: Book 8 :: Volume 73 :: Hadith 158
Narrated Abu Huraira:
The Prophet said, "Whoever believes in Allah and the Last Day, should not hurt his neighbor and whoever believes in Allah and the Last Day, should serve his guest generously and whoever believes in Allah and the Last Day, should talk what is good or keep quiet."