Proverbs 11:13-14

He who goes about as a gossip reveals secrets, but he who is trustworthy and faithful keeps a matter hidden. Where there is no (wise, intelligent) guidance, the people fall (and go off course like a ship without a helm), but in the abundance of (wise and godly) counselors there is victory.

God says repeatedly that what we say matters when we talk about ourselves and others. The tongue is powerful, and the devil will work through people if we allow it. God does not want us to fall into sin and open doors to the devil to torment our lives. God is the wisest counsel we have, and He tells us to guard our tongue.