Deuteronomy 5:20 says: You shall not bear false witness against your neighbor. Jesus says in Matthew 12:36—you must give an account on Judgment Day for every idle word you speak.
Jesus reminds us that what we say reveals what is in our hearts. What kinds of words come from your mouth? That is an indication of what your heart is really like. You can’t solve a heart problem, however, just by cleaning up your speech. You must allow the Holy Spirit to fill you with new attitudes and motives; then your speech will be cleansed at its source.