It is narrated from Imam Ali (AS) who said: There are ten characteristics in the human beings which the tongue reveals them, the tongue is a witness that reports from the inside. It is a referee that ends the disputes; questions are answered with it; an intermediator that resolves problems; articles are described with it; a commander that orders to goodness; it is an advisor that prevents badness; and relieves pains by expressing condolence; removes hostilities by being present; and a charmer that ears enjoy it [1].
[1] Kafi, Vol. 8, Page 20, Hadith 4.