In a Hadith the Holy Prophet ﷺ said;

“The thing that will make people fall face down in Hell most often will be the words that have come out of their mouth.”

It is narrated in a Hadith that a Companion (Sahabi) asked the Holy Prophet ﷺ, “O Prophet of Allah ﷺ, which is the most exalted act of worship?” He replied, “the most exalted act of worship is that your tongue always remains active with Allah’s Dhikr (remembrance).”

To protect oneself from Gheebat Hadhrat Thanvi (may Allah have mercy on him) has described a general rule which is;

“Do not say anything before reflecting on it first. It will happen sometimes that you won’t remember to think about it but if you keep reminding yourself about it, you will start remembering most of the time to think before you speak. Insha’Allah (God willing) you won’t neglect it then. Whenever you are about to say something, think first whether what you are about to say will constitute a sin. Insha’Allah this will lead to improvement.”