“careless word.” The Greek word the REV translates “careless” in Matthew 12:36 is argos (#692 ἀργός). It is a word that pertains to being unproductive and is therefore worthless, and in the context of speaking is basically a worthless word spoken carelessly (cp. BDAG Greek-English Lexicon). Some translations read “worthless” (NET), but in this context “careless” seems to be better, although we would understand what Jesus was saying even better if we understood “careless” to mean “without care,” i.e., that the person could not “care less” and thus did not care what they said and who it hurt.
The Devil’s people have no fear of God or of the Day of Judgment, so they constantly spew worthless, hurtful, ungodly language. Because unsaved people make up the majority of the people on the planet, they create an atmosphere in which people are not taught to pay attention to what they say, and so they say (or text or email) many ungodly and hurtful things. Christians beware! There is a Day of Judgment coming, and how we have used our tongue will be part of what is judged. Jesus was not kidding when he said people will be judged for what they say. Does any Christian really want to lose rewards in the coming Kingdom of Christ just so that right in the moment of emotion they can say what they feel no matter what it is or who it hurts? We Christians need to obey God and control what we say to people (Eph. 4:29). How we feel is not more important than how God commands us to behave.
[For more on the future kingdom of Christ, see Appendix 3, “Christ’s Future Kingdom on Earth.” For more on the future judgment of Christians, see commentary on 2 Cor. 5:10, “good or evil”].