Do not call someone a fool
Matthew 5:22, “But I say to you that everyone who is angry with his brother shall be guilty before the court; and whoever says to his brother, ‘You good-for-nothing,’ shall be guilty before the supreme court; and whoever says, ‘You fool,’ shall be guilty enough to go into the fiery hell.”
Calling someone a fool
Psalm 14:1, “The fool has said in his heart, “There is no God.” They are corrupt, they have committed abominable deeds; There is no one who does good”
Matthew 23:17, “You fools and blind men! Which is more important, the gold or the temple that sanctified the gold?”
When Jesus said in Matthew 5:22 that you should not call anyone a fool, contextually He was speaking of those who were unrighteously angry. That is why Jesus mentions anger in this verse. There is a righteous anger which is not sinful (Eph. 4:26, “Be angry and do not sin…” ), as well as unrighteous anger that is sinful (James 1:20, “for the anger of man does not achieve the righteousness of God”). When God is angry with someone, He is always righteous in His anger. Jesus, being God in flesh (John 1:1,14; 20:28; Col. 2:9), can righteously be angry with people and pronounce upon them the foolishness of their deeds – which He did (Matt. 23:17). Also, undoubtedly, Jesus knew Psalm 14:1 which says, “The fool has said in his heart, ‘There is no God.'” Jesus didn’t forget the well known verse, and God is not wrong for calling someone a fool, especially when it is true.
As a result, we see that the condemnation by Jesus in regards to calling someone a fool is in the context of them doing it out of unrighteous anger, not righteous anger.