How Does the Tongue Fast? By Sheikh `Aa'id Al-Qarni 
Ibn `Abbas used to say to his tongue, "O tongue! Say something good to win, or abstain from evil to be safe." Surely Allah will be merciful to those who check their utterances and weigh their words. He Almighty says [Not a word does he utter but there is a sentinel by him, ready (to note it)) (Qaf 50:18).
Every expression is recorded and every word is counted: [And your Lord is not in the least unjust to the servants) (Fussilat 41:46).
How many fasting people spoil their fasts by misusing their tongues? How can people fast and give free rein to their tongue? The purpose of fasting is not to feel hunger and thirst. It is, instead, to discipline the behavior and uplift the soul. There are, in fact, many misdeeds that emanate from the tongue if it is not properly controlled — lying, backbiting, slandering, saying obscenities, cursing, giving false evidence, insulting, and scorning.
The tongue is a means of good or evil. What a delight it would be for those who remember Allah, seek His forgiveness, praise Him, glorify Him, give thanks to Him, and always repent to Him. And what a disappointment it would be for those who use it to violate honor and sanctity and besmirch values.
O fasting people, moisten your tongue with the remembrance of Allah, discipline it with God-consciousness, and cleanse it from disobedience.