“And the tongue is a fire, a world of iniquity: so is the tongue among our members, that it defileth the whole body, and setteth on fire the course of nature; and it is set on fire of hell.” - James 3:6.
We should be very careful what we use our tongues to say because misuse of it could lead to consequences that one could hardly have imagined. When the king of the children of Ammon died, and Hanun his son ascended the throne, David decided to show kindness to him as the new king's father did to him. He then sent men to comfort the new king. However, the princes told him that the ambassadors sent by King David came with evil motive, “to search the city, and to spy it out, and to overthrow it” This was of course completely false. But the new king listened to such tales and mistreated the men sent by King David, such that the men were greatly ashamed and had to wait at Jericho until their beards were grown before returning to Jerusalem. - 2 Samuel 10:1-5.
Seeing that they had wronged the people of Israel, the Ammonites started a war by hiring soldiers from Syria to join them in fighting the Jews. However they were roundly defeated. It could be seen that so many lives and property were lost because of the abuse of the goodwill of David the king due to rash judgment. “Death and life are in the power of the tongue: and they that love it shall eat the fruit thereof.” - Proverbs 18:21.