Beloved Nabi Muhammad (Sall Allahu Alayhi Wasallam) said: "All of a human being's words count against him and not for him, except commanding the right, forbidding the wrong, and the mention of Allah Most High." [Tirmidhi]
The importance of keeping guard over what our tongue utters is so important that Beloved Nabi Muhammad (Sall Allahu Alayhi Wasallam) said that he would guarantee Paradise to whoever could control his tongue and private parts from sin. The misuse of these is a common cause of being led to Hell. When Hadrat Abu Bakr (Radhiy Allahu Anhu) heard this, he put a large stone in his mouth to prevent himself from speaking without thinking. He would take the stone out if he had to speak, but then put it in again. How far we are from the example of the Sahaabah (Companions of the Beloved Prophet)...
We should adopt silence as our modus operandi, but silence when speaking is required is not commendable. Our words count in our favour, and should be uttered, when we command the right, forbid the wrong or are engaged in the remembrance of Allah Most High. Abul Qasim Qushayri said, "Safety lies in remaining silent, which should be one's basis. Silence at the appropriate time is the mark of men, just as speech at the appropriate time is one of the finest qualities. I have heard Abu Ali Daqqaq say, 'He who is silent when something should be said is a tongue-less villain.'" [Reliance of the Traveller by Ahmad ibn Naqib al-Misri]
“All that is required for the triumph of evil is for good men to remain silent.”