“ speak a good word or remain silent ”
―Prophet Muhammad ﷺ
Riyad as-Salihin 18, Hadith 1

The Quran instructs Muslims to speak in the following manners :

(Speak kindly) Quran 2:83

(Speak truthfully) Quran 3:17

(Speak justly) Quran 6:152

(Speak graciously) Quran 17:23

(Speak fairly) Quran 17:28

(Speak politely) Quran 17:53