[Numbers] 35:33 Murderers were to be executed because they corrupted the land. But Jesus startles us by saying that even being angry at someone can be a sin like murder. (Matthew 521-22). Murder and anger stem from the same root. While one seems a lesser sin, it will often lead to more sin. Unchecked bitterness and anger will ultimately destroy us. We need to deal with these strong emotions in an appropriate way before they fester and corrupt our life.
Student's Life Application Bible