Collection of Hadeith

Narrated 'Abdullah bin 'Amr: The Prophet never used bad language neither a "Fahish nor a Mutafahish. He used to say "The best amongst you are those who have the best manners and character." (Bukhari, volume 4, book 56, Number 759)

1734. Ibn Mas`ud (May Allah be pleased with him) said: The Messenger of Allah (PBUH) said, "A true believer does not taunt or curse or abuse or talk indecently.''
[At-Tirmidhi].

The Prophet (sal Allahu alayhi wa sallam) 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]

Commentary:
The importance of keeping guard over what our tongue utters is so important that the Prophet (sal Allahu alaihi wa sallam) 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 Jahannum. When Hazrat Abu Bakr (radi 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 Sahabah...

We should adopt silence as our modus operandi, but silence when speaking is required is not commendable. Our words count in our favor, 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 tongueless villain.'" [r 1.1: 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.”