No one will disagree that murder is bad and unlawful. But Jesus extends the law in a very stringent way. It may even be more stringent for disciples today than it was for disciples in the original audience.
Jesus wants us to watch even our internal attitudes toward others. If we harbor attitudes that demean others in our own minds, the attitudes may issue in some kind of action. Yes, saying something is an action. No hiding behind “it’s only words.”
Jesus is not the least bit afraid to extend the Word of God with his own word. That should tell us something about his self-understanding.
Earthly courts will not judge us on our attitudes. They might judge us on our words in certain circumstances. The heavenly court is looking on our hearts.
Acting in anger is something we should never, ever do. Cool down first and use your noodle.
Furthermore, our relationship with God is somehow dependent on our relationships with others. In this passage, reconciliation is seen as more important than worship. Imagine that.
God knows what we are made of. Let’s allow him to remake us into a better form of what we are.