Professor Ansarian:
One of Allah,s greatest blessings and his delicate creation is tongue. The tongue,s weight is less but its crime and obedience is immense and gigantic. Tongue can cause the utmost obedience and rebellion for a servant. If we want to calculate the obedience and worships and also evaluate the sins we commit, then we will get that the majority of the sins and worships are done by the tongue. So we must too sensitive and careful about this very tiny organ and fear the consequences of its freedom and Promiscuity because the hardest and worst torment and punishment in the hell is for the tongue.
source : erfan.ir