Sahih Muslim Book 1, Hadith Number 76.

Chapter : Concerning exhortation to accord honour and respect to the neighbour and the guest and obligation to observe silence except in goodness, and all these qualities come within the orbit of Iman.

It is reported on the authority of Abu Huraira that the Messenger of Allah (may peace and blessings be upon him) observed: He who believes in Allah and the Last Day does not harm is neighbour, and he who believes in Allah and the Last Day shows hospitality to his guest and he who believes in Allah and the Last Day speaks good or remains silent.