Silence is golden. Islam encourages us to speak what is good and beneficial; at the same time cautioning us to be careful in what we say, lest we say something that is harmful or false. Shaykh Kamal El Mekki talks about this further in this video.
The Muslim has to guard his tongue and avoid things that have been forbidden. Among these forbidden things which people often take lightly are gheebah (backbiting), buhtan (slander) and nameemah (malicious gossip).