Almighty Allah says:

'O you who believe! Be conscious of Allah, and speak in a straightforward manner. He will rectify your conduct for you, and will forgive you your sins. Whoever obeys Allah and His Messenger has won a great victory.' (Surah al-Ahzab, 70-71)

Allah informs us in the Quran some of what constitutes good in our speech and benefits other people.

Abu Hurayrah radiallahu anhu reports:

Allah’s Messenger peace be upon him said: “Whoever believes in Allah and the Last Day should speak a good word or remain silent. And whoever believes in Allah and the Last Day should show hospitality to his neighbor.  And whoever believes in Allah and the Last Day should show hospitality to his guest.”

This hadith shows some of the ways that a Muslim’s faith should affect the way he relates to others. It indicates three matters, and in doing so it brings together everything that good manners entail with respect to both word and deed.