The importance of correction of tongue is made clearer when we know that a large part of sins as a large part of good deeds are performed by tongue.
Ghazali has narrated twenty types of vices and sins for tongue as follows:
1- Speaking about the affairs not concerned with man.
2- Rant and babbling
3- Speaking about forbidden affairs like description of meetings of wine, gambling and unchaste women.
4- Dispute and fussing (caviling and objecting others for wrong purposes as humiliating them or one's own pedantry).
5- Enmity and affray and quarrel in utterance
6- Affectation in speech and trouble in rhythm and such like
7- Abuse and insult
8- Cursing
9- Profane singing and unsound sings
10- Indulgence in humor
11- Irony and mockery
12- Disclosing mysteries of others
13- Lie promise
14- Lie in speech and oath
15- Slander
16- Gossip
17- Hypocrisy in speech
18- Inappropriate eulogy
19- Negligence from speech's elegance and tools and mistakes thereof
20- Vulgarians' questions in respect to complicated issues related to beliefs, which can not understand them
Surely, pests and vices of tongue are not restricted to what Ghazali has numerated. For instance, following affairs are among the vices of tongue, which are not stated by him:
1- Accusation
2- False evidence
3- Self-admiration
4- Spreading fornication and unfounded rumors and roorbach, although being mentioned as a probability
5- Harshness in utterance
6- Improper insist (like Children of Israel, and etc)
7- Molestation of others with one's speech
8- Blaming one who is not despicable
9- Ungratefulness with tongue
10- False propagation and encourage to sin There is no doubt that correction of tongue should be studied and taught as one of the most critical moral issues.
The importance of this subject is made clear when we consider this fact that tongue is the simplest and easiest and cheapest means available for man, and its speedy function is not comparable with anything else, and so we shall be very careful of it, and in this view, we can resemble it to the useful materials having an explosive power and capability. As man takes care of them attentively, he should always be watchful to this sensible organ.