Sermon on the Mount

21 "You have heard that it was said to the people long ago, ‘You shall not murder,[a] and anyone who murders will be subject to judgment.’ 22 But I tell you that anyone who is angry with a brother or sister[b][c] will be subject to judgment. Again, anyone who says to a brother or sister, ‘Raca,’[d] is answerable to the court. And anyone who says, ‘You fool!’ will be in danger of the fire of hell.
23 "Therefore, if you are offering your gift at the altar and there remember that your brother or sister has something against you, 24 leave your gift there in front of the altar. First go and be reconciled to them; then come and offer your gift.
25 "Settle matters quickly with your adversary who is taking you to court. Do it while you are still together on the way, or your adversary may hand you over to the judge, and the judge may hand you over to the officer, and you may be thrown into prison.

Jesus goes to the heart of the OT law here, as he does throughout the Sermon on the Mount. The issue with legal transgressions, like adultery or divorce, is not what we do but what fills us and leads to these actions. A heart transplant is required, not a plaster over an obvious wound.
The purpose of the Gospel of Matthew is to provoke us to ask, "Who is Jesus?" His divine identity is revealed in the first chapter and confirmed by significant witnesses. Then we read this distillation of his ethical teaching - which includes the impossible command to "be perfect as your Father in Heaven is perfect" (5:48). And this is followed by some humungous miracles (chapters 8-9). All of this is meant to provoke questions like, "Has anyone else lived a life like this" and "who has supernatural power of this kind?" Only Jesus lives this life and exercises this power.

And he alone has the power to change the heart.

Everyone has called another person "raca" or "fool" (22). Everyone has nurtured anger in their heart. Everyone fails to immediately sort things out with friend and foe alike (23-25). The only exception to this in history is Jesus who not only readily forgave again and again but also uniquely refused to nurture feelings of internal violence towards others in his heart.
The problem with these feelings (like lust or greed) is that they have the capacity to fill our hearts - and anything that fills us can control what we do. This is why we are told not to be drunk with wine, for example, but to be filled with the Spirit (Ephesians 5:18).

Meditation

Ask yourself, when you are angry with someone, who is in a prison? How do you release yourself?