"When man wakes up in the morning each day, all parts of the body warn the TONGUE saying, Fear God as regards us, for we are at your mercy; if you are upright, we will be upright and if you are crooked, we become crooked." (At-Tirmidhee)
This is an excellent example of how the tongue works. InshaAllah I will try to put this in a very easy to understand form for all.

Only that which you put into it. Therefore if you put water inside, only water would come out, if you put blood inside, only blood would come out, if you put Zamzam inside, only Zamazam would come out, if you put dirty water inside, only dirty water will come out.
Now lets take a look at a vital organ, The Heart. The heart is the same as the water pot, What ever you put inside, the same shall come out. Let us becareful as to what we do, what we see, what we feel, how we behave, etc etc.

So what ever we take in and absorb will one day come out.
And how will it come out? The Tongue!

The weapon of Mass destruction
I have tried to keep it as simple as possible, but one can go into some great depth in their explanation of this
This is something I had put together and framed. I have stuck it up in my house near the front door / mirror as a reminder to my self and to those who read it, InshaAllah.
And why did you not, when you heard it, say? "It is not right of us to speak of this: Glory to God, this is a most serious slander" (Quran 24:16)
"When man wakes up in the morning each day, all parts of the body warn the tongue saying, Fear God as regards us for we are at your mercy; if you are upright, we will be upright and if you are crooked, we become crooked." (At-Tirmidhee)
The Prophet (peace be upon him) defines backbiting in the following way, and his definition is preferred over any other:
He said: Do you know what backbiting is?
They (the campanions) said: Allah and His Messenger know best.
He said: It is to mention about your brother something that he would dislike having mentioned about him. [Sahîh Muslim (2589)]
`Âishah relates that she said to the Prophet (peace be upon him): It should tell you enough about Safiyyah that she is short.
To this he replied: You have said a word that if it was to be mixed with the water of the sea, it would contaminate it. [Sunan al-Tirmidhî (2502) and Sunan Abî Dâwûd (4875)]
The Prophet (SAS) has clearly stated, "The gossip-monger will not enter paradise" (Bukhari, Muslim).