The Old Testament law taught that crimes such as slander and murder were wrong. But Jesus went beyond these actions to the thought, motives, or words behind them.
Raca was a term of contempt meaning “empty one” or “vain fellow.” Anyone who uttered this word against another person could be charged with slander before the Jewish Council, or the Sanhedrin.
But according to Jesus, to call someone a fool was an even more serious offense. This was a way of uttering a curse against a person and consigning his soul to hell. Anyone who did this was in danger of being sent to the very punishment he wished upon another.
MATTHEW 5:22- Whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire.