Matthew 5:21-22
Jesus teaches about anger
21 Jesus then said, ‘You know the commands that God gave to your ancestors: “You must not murder anyone. Anyone who does murder will stand in front of a judge. The judge will punish him because he has done a wrong thing.” 22 But what I now say to you is this. Anybody who is angry with his brother will have to stand in front of a judge. If someone calls his brother by a bad name, he will have to stand in front of the Jewish leaders. They will judge him. But if someone says to his brother, “You are a useless fool,” that person deserves punishment in the fires of hell.
5:22‘Brother’ probably means any friend or other person that you know.